Second Ig-like domain of Junctional adhesion molecule-1 (JAM1); a member of the I-set of IgSF domains; The members here are composed of the second Ig-like domain of Junctional adhesion molecule-1 (JAM1). JAM1 is an immunoglobulin superfamily (IgSF) protein with two Ig-like domains in its extracellular region; it plays a role in the formation of endothelial and epithelial tight junction and acts as a receptor for mammalian reovirus sigma-1. The IgSF is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. The two sheets are linked together by a conserved disulfide bond between B strand and F strand. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The second Ig-like domain of JAM1 is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, the A strand of the I-set is discontinuous but lacks a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 135 PTVNIPSSATIGNRAVLTCSEQDGSPPSEYTWFKDGIVMPTNPKSTRAFSNSSYVLNPTTGELVFDPLSASDTGEYSCEA 214
Cdd:cd20950   1 PTVNIPSSATIGNRAVLTCSEPDGSPPSEYTWFKDGVVMPTNPKSTRAFSNSSYSLDPTTGELVFDPLSASDTGEYSCEA 80

                        90
                ....*....|....*..
gi 10720061 215 RNGYGTPMTSNAVRMEA 231
Cdd:cd20950  81 RNGYGTPMRSNAVRMEA 97

Second Ig-like domain of Junctional adhesion molecule-1 (JAM1); a member of the I-set of IgSF domains; The members here are composed of the second Ig-like domain of Junctional adhesion molecule-1 (JAM1). JAM1 is an immunoglobulin superfamily (IgSF) protein with two Ig-like domains in its extracellular region; it plays a role in the formation of endothelial and epithelial tight junction and acts as a receptor for mammalian reovirus sigma-1. The IgSF is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. The two sheets are linked together by a conserved disulfide bond between B strand and F strand. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The second Ig-like domain of JAM1 is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, the A strand of the I-set is discontinuous but lacks a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 135 PTVNIPSSATIGNRAVLTCSEQDGSPPSEYTWFKDGIVMPTNPKSTRAFSNSSYVLNPTTGELVFDPLSASDTGEYSCEA 214
Cdd:cd20950   1 PTVNIPSSATIGNRAVLTCSEPDGSPPSEYTWFKDGVVMPTNPKSTRAFSNSSYSLDPTTGELVFDPLSASDTGEYSCEA 80

                        90
                ....*....|....*..
gi 10720061 215 RNGYGTPMTSNAVRMEA 231
Cdd:cd20950  81 RNGYGTPMRSNAVRMEA 97

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061     36 PEVRIPENNPVKLSCAYSGFSSPRVEWKFDQGdttRLVCYNNKITASYEDRVTFLptgiTFKSVTREDTGTYTCMVSEEG 115
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPPPEVTWYKQGG---KLLAESGRFSVSRSGSTSTL----TISNVTPEDSGTYTCAATNSS 74

                           90
                   ....*....|
gi 10720061    116 GNSYGEVKVK 125
Cdd:smart00410  75 GSASSGTTLT 84

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 10720061    142 SATIGNRAVLTCsEQDGSPPSEYTWFKDGIVMPTNPKSTRAFSNSsyvlnpTTGELVFDPLSASDTGEYSCEARNGYGT 220
Cdd:smart00410   5 TVKEGESVTLSC-EASGSPPPEVTWYKQGGKLLAESGRFSVSRSG------STSTLTISNVTPEDSGTYTCAATNSSGS 76

Second Ig-like domain of Junctional adhesion molecule-1 (JAM1); a member of the I-set of IgSF domains; The members here are composed of the second Ig-like domain of Junctional adhesion molecule-1 (JAM1). JAM1 is an immunoglobulin superfamily (IgSF) protein with two Ig-like domains in its extracellular region; it plays a role in the formation of endothelial and epithelial tight junction and acts as a receptor for mammalian reovirus sigma-1. The IgSF is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. The two sheets are linked together by a conserved disulfide bond between B strand and F strand. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The second Ig-like domain of JAM1 is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, the A strand of the I-set is discontinuous but lacks a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 135 PTVNIPSSATIGNRAVLTCSEQDGSPPSEYTWFKDGIVMPTNPKSTRAFSNSSYVLNPTTGELVFDPLSASDTGEYSCEA 214
Cdd:cd20950   1 PTVNIPSSATIGNRAVLTCSEPDGSPPSEYTWFKDGVVMPTNPKSTRAFSNSSYSLDPTTGELVFDPLSASDTGEYSCEA 80

                        90
                ....*....|....*..
gi 10720061 215 RNGYGTPMTSNAVRMEA 231
Cdd:cd20950  81 RNGYGTPMRSNAVRMEA 97

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061     36 PEVRIPENNPVKLSCAYSGFSSPRVEWKFDQGdttRLVCYNNKITASYEDRVTFLptgiTFKSVTREDTGTYTCMVSEEG 115
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPPPEVTWYKQGG---KLLAESGRFSVSRSGSTSTL----TISNVTPEDSGTYTCAATNSS 74

                           90
                   ....*....|
gi 10720061    116 GNSYGEVKVK 125
Cdd:smart00410  75 GSASSGTTLT 84

Immunoglobulin domain; The members here are composed of the immunoglobulin (Ig) domain found in the Ig superfamily. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, including T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, including butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E, and D strands in one sheet and A', G, F, C, C' and C" in the other. The structures in C1-set are smaller than those in the V-set; they have one beta sheet that is formed by strands A, B, E, and D and the other by strands G, F, C, and C'. Moreover, a C1-set Ig domain contains a short C' strand (three residues) and lacks A' and C" strand. Unlike other Ig domain sets, C2-set structures do not have a D strand. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 10720061 149 AVLTCSEQdGSPPSEYTWFKDGIVMPTNPKSTRAFSNSSyvlnpttGELVFDPLSASDTGEYSCEARNGYGTPMTSNA 226
Cdd:cd00096   1 VTLTCSAS-GNPPPTITWYKNGKPLPPSSRDSRRSELGN-------GTLTISNVTLEDSGTYTCVASNSAGGSASASV 70

Sixth immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the sixth immunoglobulin domain of the Drosophila melanogaster Down syndrome cell adhesion molecule (DSCAM) protein and similar proteins. Down syndrome cell adhesion molecule (DSCAM) is a cell adhesion molecule that plays critical roles in neural development, including axon guidance and branching, axon target recognition, self-avoidance and synaptic formation. DSCAM belongs to the immunoglobulin superfamily and contributes to defects in the central nervous system in Down syndrome patients. Vertebrate DSCAMs differ from Drosophila Dscam1 in that they lack the extensive alternative splicing that occurs in the insect gene. Drosophila melanogaster Dscam has 38,016 isoforms generated by the alternative splicing of four variable exon clusters, which allows every neuron in the fly to display a distinctive set of Dscam proteins on its cell surface. Drosophila Dscam1 is a cell-surface protein that plays important roles in neural development and axon tiling of neurons. It is shown that thousands of isoforms bind themselves through specific homophilic (self-binding) interactions, a process which mediates cellular self-recognition. Drosophila Dscam2 is also alternatively spliced and plays a key role in the development of two visual system neurons, monopolar cells L1 and L2. This group is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 10720061 143 ATIGNRAVLTCSEQDGSPPSEYTWFKDGIVMPTNpkstRAFSNSSyvLNPTTGELVFDPLSASDTGEYSCEARNGYG 219
Cdd:cd20959  14 AQVGMRAQLHCGVPGGDLPLNIRWTLDGQPISDD----LGITVSR--LGRRSSILSIDSLEASHAGNYTCHARNSAG 84

Fifth immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fifth immunoglobulin domain of the Drosophila melanogaster Down syndrome cell adhesion molecule (DSCAM) protein and similar proteins. Down syndrome cell adhesion molecule (DSCAM) is a cell adhesion molecule that plays critical roles in neural development, including axon guidance and branching, axon target recognition, self-avoidance and synaptic formation. DSCAM belongs to the immunoglobulin superfamily and contributes to defects in the central nervous system in Down syndrome patients. Vertebrate DSCAMs differ from Drosophila Dscam1 in that they lack the extensive alternative splicing that occurs in the insect gene. Drosophila melanogaster Dscam has 38,016 isoforms generated by the alternative splicing of four variable exon clusters, which allows every neuron in the fly to display a distinctive set of Dscam proteins on its cell surface. Drosophila Dscam1 is a cell-surface protein that plays important roles in neural development and axon tiling of neurons. It is shown that thousands of isoforms bind themselves through specific homophilic (self-binding) interactions, a process which mediates cellular self-recognition. Drosophila Dscam2 is also alternatively spliced and plays a key role in the development of two visual system neurons, monopolar cells L1 and L2. This group is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 131 PPS-KPTVNIpsSATIGNRAVLTCSEQdGSPPSEYTWFKDGIVMPTNPKStRAFSNssyvlnpttGELVFDPL-SASDTG 208
Cdd:cd20958   1 PPFiRPMGNL--TAVAGQTLRLHCPVA-GYPISSITWEKDGRRLPLNHRQ-RVFPN---------GTLVIENVqRSSDEG 67

                        90
                ....*....|....*..
gi 10720061 209 EYSCEARNGYGTPMTSN 225
Cdd:cd20958  68 EYTCTARNQQGQSASRS 84

Immunoglobulin domain; Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include antibodies, the giant muscle kinase titin and receptor tyrosine kinases. Immunoglobulin-like domains may be involved in protein-protein and protein-ligand interactions.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061   137 VNIPSSATIGNRAVLTCSEQDGSPPSEYTWFKDGIVMPTNPKSTRAFSNSsyvlnpTTGELVFDPLSASDTGEYSCEARN 216
Cdd:pfam00047   2 APPTVTVLEGDSATLTCSASTGSPGPDVTWSKEGGTLIESLKVKHDNGRT------TQSSLLISNVTKEDAGTYTCVVNN 75

Second immunoglobulin (Ig)-like domain in Robo (roundabout) receptors; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin (Ig)-like domain in Robo (roundabout) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of the Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, and Robo3), and three mammalian Slit homologs (Slit-1,Slit-2, Slit-3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit-1, Slit-2, Slit-3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit-2 has been shown by surface plasmon resonance experiments and mutational analysis to be the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 140 PSS--ATIGNRAVLTCSEQDGSPPSEYTWFKDGIvmPTNPKSTRafsnssyVLNPTTGELVFDPLSASDTGEYSCEARNG 217
Cdd:cd05724   4 PSDtqVAVGEMAVLECSPPRGHPEPTVSWRKDGQ--PLNLDNER-------VRIVDDGNLLIAEARKSDEGTYKCVATNM 74

                ...
gi 10720061 218 YGT 220
Cdd:cd05724  75 VGE 77

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061    38 VRIPENNPVKLSCAYSGFSSPRVEWKFDQGDTTRlvcyNNKITASYEDRVTFLptgiTFKSVTREDTGTYTCMVSeeggN 117
Cdd:pfam07679  10 VEVQEGESARFTCTVTGTPDPEVSWFKDGQPLRS----SDRFKVTYEGGTYTL----TISNVQPDDSGKYTCVAT----N 77

                          90
                  ....*....|...
gi 10720061   118 SYGEVKVKLIVLV 130
Cdd:pfam07679  78 SAGEAEASAELTV 90

Fourth Ig domain of the neural cell adhesion molecule contactin-2, and similar domains; The members here are composed of the fourth Ig domain of the neural cell adhesion molecule contactin-2. Contactins are comprised of six Ig domains followed by four fibronectin type III (FnIII) domains anchored to the membrane by glycosylphosphatidylinositol. Contactin-2 (also called TAG-1, axonin-1) facilitates cell adhesion by homophilic binding between molecules in apposed membranes. The first four Ig domains form the intermolecular binding fragment which arranges as a compact U-shaped module by contacts between Ig domains 1 and 4, and domains 2 and 3. It has been proposed that a linear zipper-like array forms, from contactin-2 molecules alternatively provided by the two apposed membranes.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 10720061 158 GSPPSEYTWFKDGIVMPTnpkstrafSNSSYVLNpttGELVFDPLSASDTGEYSCEARNGYGT 220
Cdd:cd05728  25 GNPRPAYRWLKNGQPLAS--------ENRIEVEA---GDLRITKLSLSDSGMYQCVAENKHGT 76

Immunoglobulin domain; Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include antibodies, the giant muscle kinase titin and receptor tyrosine kinases. Immunoglobulin-like domains may be involved in protein-protein and protein-ligand interactions.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061    33 SSEPEVRIPENNPVKLSCAYSGFSS-PRVEWKFD--QGDTTRLVCYNNKITASyedrvtflpTGITFKSVTREDTGTYTC 109
Cdd:pfam00047   1 SAPPTVTVLEGDSATLTCSASTGSPgPDVTWSKEggTLIESLKVKHDNGRTTQ---------SSLLISNVTKEDAGTYTC 71

                          90
                  ....*....|....*
gi 10720061   110 MVSEEGGNSYGEVKV 124
Cdd:pfam00047  72 VVNNPGGSATLSTSL 86

Immunoglobulin (Ig)-like domain of human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) domains 2, 4, and 6, and similar domains; The members here are composed of the second, fourth, and sixth immunoglobulin (Ig)-like domains in human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) protein subfamily. The CEA family is a group of anchored or secreted glycoproteins expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions; it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two [D1, D4] or four [D1-D4] Ig-like domains on the cell surface.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 134 KPTVNIPSSATIGNR--AVLTCSEQDgsPPSEYTWFKDGIVMPTNPKSTrafsnssyvLNPTTGELVFDPLSASDTGEYS 211
Cdd:cd05740   1 KPFISSNNSNPVEDKdaVTLTCEPET--QNTSYLWWFNGQSLPVTPRLT---------LSNGNRTLTLLNVTREDAGAYQ 69

                ....*
gi 10720061 212 CEARN 216
Cdd:cd05740  70 CEISN 74

Immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM) and similar proteins; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the first immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM). L1 belongs to the L1 subfamily of cell adhesion molecules (CAMs) and is comprised of an extracellular region having six Ig-like domains and five fibronectin type III domains, a transmembrane region and an intracellular domain. L1 is primarily expressed in the nervous system and is involved in its development and function. L1 is associated with an X-linked recessive disorder, X-linked hydrocephalus, MASA syndrome, or spastic paraplegia type 1, that involves abnormalities of axonal growth. This group also contains NrCAM [Ng(neuronglia)CAM-related cell adhesion molecule], which is primarily expressed in the nervous system, and human neurofascin. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lacks a C" strand.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 150 VLTCsEQDGSPPSEYTWFKDGIvmPTNPKStrafsNSSYVLNPTTGELVFDPLSASDT---GEYSCEARNGYGTPMTSNA 226
Cdd:cd05733  20 TIKC-EAKGNPQPTFRWTKDGK--FFDPAK-----DPRVSMRRRSGTLVIDNHNGGPEdyqGEYQCYASNELGTAISNEI 91

                .
gi 10720061 227 V 227
Cdd:cd05733  92 R 92

Immunoglobulin (Ig)-like domain of NrCAM (Ng (neuronglia) CAM-related cell adhesion molecule); member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the first immunoglobulin (Ig)-like domain of NrCAM (Ng (neuronglia) CAM-related cell adhesion molecule). NrCAM belongs to the L1 subfamily of cell adhesion molecules (CAMs) and is comprised of an extracellular region having six Ig-like domains and five fibronectin type III domains, a transmembrane region, and an intracellular domain. NrCAM is primarily expressed in the nervous system.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 150 VLTCsEQDGSPPSEYTWFKDG--IVMPTNPKSTrafsnssyvLNPTTGELVFDPLSASDT----GEYSCEARNGYGTPMT 223
Cdd:cd05874  20 VIQC-EAKGKPPPSFSWTRNGthFDIDKDPKVT---------MKPNTGTLVINIMNGEKAeayeGVYQCTARNERGAAVS 89

                ....
gi 10720061 224 SNAV 227
Cdd:cd05874  90 NNIV 93

First immunoglobulin (Ig)-like domain of Tyro3 receptor tyrosine kinase (RTK), and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain of Tyro3 receptor tyrosine kinase (RTK). Tyro3 together with Axl and Mer form the Axl/Tyro3 family of receptor tyrosine kinases (RTKs). This family includes Axl (also known as Ark, Ufo, and Tyro7), Tyro3 (also known as Sky, Rse, Brt, Dtk, and Tif), and Mer (also known as Nyk, c-Eyk, and Tyro12). Axl/Tyro3 family receptors have an extracellular portion with two Ig-like domains followed by two fibronectin-types III (FNIII) domains, a membrane-spanning single helix, and a cytoplasmic tyrosine kinase domain. Axl, Tyro3 and Mer are widely expressed in adult tissues, though they show higher expression in the brain, in the lymphatic and vascular systems, and in the testis. Axl, Tyro3, and Mer bind the vitamin K dependent protein Gas6 with high affinity, and in doing so activate their tyrosine kinase activity. Axl/Gas6 signaling may play a part in cell adhesion processes, prevention of apoptosis, and cell proliferation.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061  37 EVRIPENNPVKLSCAYSGFSSPRVEWKFDQGDTTRLvcYNNKITASYEDRVTFLptgiTFKSVTREDTGTYTCMVsEEGG 116
Cdd:cd20961   2 KLTVSQGQPVKLNCSVEGMEEPDIQWVKDGAVVQNL--DQLYIPVSEQHWIGFL----SLKSVERSDAGRYWCQV-EDGG 74

                ..
gi 10720061 117 NS 118
Cdd:cd20961  75 ET 76

Immunoglobulin domain; This domain contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061   140 PSSATIGNRAVLTCSeQDGSPPSEYTWFKDGIVMPTNPKStraFSNSsyvlnpttgelvfdpLSASDTGEYSCEARNGYG 219
Cdd:pfam13895   8 PTVVTEGEPVTLTCS-APGNPPPSYTWYKDGSAISSSPNF---FTLS---------------VSAEDSGTYTCVARNGRG 68

                  ....*....
gi 10720061   220 tPMTSNAVR 228
Cdd:pfam13895  69 -GKVSNPVE 76

Second immunoglobulin (Ig)-like domain of protein tyrosine kinase (PTK) 7; The members here are composed of the second immunoglobulin (Ig)-like domain in protein tyrosine kinase (PTK) 7, also known as CCK4. PTK7 is a subfamily of the receptor protein tyrosine kinase family, and is referred to as an RPTK-like molecule. RPTKs transduce extracellular signals across the cell membrane and play important roles in regulating cell proliferation, migration, and differentiation. PTK7 is organized as an extracellular portion having seven Ig-like domains, a single transmembrane region, and a cytoplasmic tyrosine kinase-like domain. PTK7 is considered a pseudokinase as it has several unusual residues in some of the highly conserved tyrosine kinase (TK) motifs; it is predicted to lack TK activity. PTK7 may function as a cell-adhesion molecule. PTK7 mRNA is expressed at high levels in placenta, melanocytes, liver, lung, pancreas, and kidney. PTK7 is overexpressed in several cancers, including melanoma and colon cancer lines.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 127 IVLVPPSKPTVNIPSSatignRAVLTCsEQDGSPPSEYTWFKDGIVMPTnpkstrafSNSSYVLNPTTGELVFDPLSASD 206
Cdd:cd05760   2 VVLKHPASAAEIQPSS-----RVTLRC-HIDGHPRPTYQWFRDGTPLSD--------GQGNYSVSSKERTLTLRSAGPDD 67

                        90
                ....*....|....
gi 10720061 207 TGEYSCEARNGYGT 220
Cdd:cd05760  68 SGLYYCCAHNAFGS 81

Seventh immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the seventh immunoglobulin domain of the Drosophila melanogaster Down syndrome cell adhesion molecule (DSCAM) protein and similar proteins. Down syndrome cell adhesion molecule (DSCAM) is a cell adhesion molecule that plays critical roles in neural development, including axon guidance and branching, axon target recognition, self-avoidance and synaptic formation. DSCAM belongs to the immunoglobulin superfamily and contributes to defects in the central nervous system in Down syndrome patients. Vertebrate DSCAMs differ from Drosophila Dscam1 in that they lack the extensive alternative splicing that occurs in the insect gene. Drosophila melanogaster Dscam has 38,016 isoforms generated by the alternative splicing of four variable exon clusters, which allows every neuron in the fly to display a distinctive set of Dscam proteins on its cell surface. Drosophila Dscam1 is a cell-surface protein that plays important roles in neural development and axon tiling of neurons. It is shown that thousands of isoforms bind themselves through specific homophilic (self-binding) interactions, a process which mediates cellular self-recognition. Drosophila Dscam2 is also alternatively spliced and plays a key role in the development of two visual system neurons, monopolar cells L1 and L2. This group is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061  35 EPE-VRIPENNPVKLSCAYSGFSSPRVEWKFDQGDTTrlvcyNNKITASYEDRVTFLPTG-ITFKSVTREDTGTYTCmvs 112
Cdd:cd20954   7 EPVdANVAAGQDVMLHCQADGFPTPTVTWKKATGSTP-----GEYKDLLYDPNVRILPNGtLVFGHVQKENEGHYLC--- 78

                        90
                ....*....|....*..
gi 10720061 113 eEGGNSYGEVKVKLIVL 129
Cdd:cd20954  79 -EAKNGIGSGLSKVIFL 94

Immunoglobulin (Ig)-like domain of titin and similar proteins; The members here are composed of the immunoglobulin (Ig)-like domain found in titin-like proteins and similar proteins. Titin (also called connectin) is a fibrous sarcomeric protein specifically found in vertebrate striated muscle. Titin is a giant protein; depending on isoform composition, it ranges from 2970 to 3700 kDa, and is of a length that spans half a sarcomere. Titin largely consists of multiple repeats of Ig-like and fibronectin type 3 (FN-III)-like domains. Titin connects the ends of myosin thick filaments to Z disks and extends along the thick filament to the H zone. It appears to function similarly to an elastic band, keeping the myosin filaments centered in the sarcomere during muscle contraction or stretching. Within the sarcomere, titin is also attached to or is associated with myosin binding protein C (MyBP-C). MyBP-C appears to contribute to the generation of passive tension by titin and like titin has repeated Ig-like and FN-III domains. Also included in this group are worm twitchin and insect projectin, thick filament proteins of invertebrate muscle which also have repeated Ig-like and FN-III domains.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061  38 VRIPENNPVKLSCAYSGFSSPRVEWKFDQGDTTRLVCYNNKITASYedrvtflpTGITFKSVTREDTGTYTCMVSeeggN 117
Cdd:cd05748   2 IVVRAGESLRLDIPIKGRPTPTVTWSKDGQPLKETGRVQIETTASS--------TSLVIKNAKRSDSGKYTLTLK----N 69

                        90
                ....*....|...
gi 10720061 118 SYGEVKVKLIVLV 130
Cdd:cd05748  70 SAGEKSATINVKV 82

First immunoglobulin (Ig)-like constant domain in Robo (roundabout) receptors, and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain in Roundabout (Robo) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, and Robo3), and three mammalian Slit homologs (Slit1, Slit2, Slit3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit1, Slit2,and Slit3 are expressed at the ventral midline. Robo3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 140 PSSATI--GNRAVLTCsEQDGSPPSEYTWFKDGivmptNPKSTRAFSNSSYVLNPTTGELVFDPL-----SASDTGEYSC 212
Cdd:cd07693   7 PSDLIVskGDPATLNC-KAEGRPTPTIQWLKNG-----QPLETDKDDPRSHRIVLPSGSLFFLRVvhgrkGRSDEGVYVC 80

                        90
                ....*....|....
gi 10720061 213 EARNGYGTPMTSNA 226
Cdd:cd07693  81 VAHNSLGEAVSRNA 94

Fourth Ig-like domain from smooth muscle myosin light chain kinase and similar domains ; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain from smooth muscle myosin light chain kinase (MYLK) and similar domains. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of this group shows that the fourth Ig-like domain from myosin light chain kinase lacks this strand and thus belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 131 PPSKPTVNIPSSATIGNRAVLTCSEQdGSPPSEYTWFKDGivMPTNPKSTRafsnssYVLNPTTGELVFDPLSASDTGEY 210
Cdd:cd20976   1 APSFSSVPKDLEAVEGQDFVAQCSAR-GKPVPRITWIRNA--QPLQYAADR------STCEAGVGELHIQDVLPEDHGTY 71

                        90
                ....*....|
gi 10720061 211 SCEARNGYGT 220
Cdd:cd20976  72 TCLAKNAAGQ 81

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor_like-1(FGFRL1); member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor like-1(FGFRL1). FGFRL1 is comprised of a signal peptide, three extracellular Ig-like modules, a transmembrane segment, and a short intracellular domain. FGFRL1 is expressed preferentially in skeletal tissues. Similar to FGF receptors, the expressed protein interacts specifically with heparin and with FGF2. FGFRL1 does not have a protein tyrosine kinase domain at its C-terminus; neither does its cytoplasmic domain appear to interact with a signaling partner. It has been suggested that FGFRL1 may not have any direct signaling function, but instead acts as a decoy receptor trapping FGFs and preventing them from binding other receptors.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061  41 PENNPVKLSCAYSGFSSPRVEWKFDQgdtTRLVcyNNKITASYEDRVTflptgITFKSVTREDTGTYTCMVSEEGG--NS 118
Cdd:cd05856  17 PVGSSVRLKCVASGNPRPDITWLKDN---KPLT--PPEIGENKKKKWT-----LSLKNLKPEDSGKYTCHVSNRAGeiNA 86

                ....*.
gi 10720061 119 YGEVKV 124
Cdd:cd05856  87 TYKVDV 92

Fifth Ig-like domain of Roundabout (Robo) homolog 1/2, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fifth Ig-like domain of Roundabout (Robo) homolog 1/2 and similar domains. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, -2, and -3), and three mammalian Slit homologs (Slit-1,-2, -3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, -2, and -3 are expressed by commissural neurons in the vertebrate spinal cord and Slits 1, -2, -3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of slit responsiveness, antagonizes slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. The fifth Ig-like domain of Robo 1 and 2 is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 127 IVLVPPSKPTVnipssaTIGNRAVLTCSEQdGSPPSEYTWFKDGIVMPTNPKSTRAFSNssyvlnpttGELVFDPLSASD 206
Cdd:cd20952   1 IILQGPQNQTV------AVGGTVVLNCQAT-GEPVPTISWLKDGVPLLGKDERITTLEN---------GSLQIKGAEKSD 64

                        90
                ....*....|....
gi 10720061 207 TGEYSCEARNGYGT 220
Cdd:cd20952  65 TGEYTCVALNLSGE 78

Third immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule 1 (NCAM-1); member of the I-set of IgSF domains; The members here are composed of the third immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule (NCAM-1). NCAM plays important roles in the development and regeneration of the central nervous system, in synaptogenesis and neural migration. NCAM mediates cell-cell and cell-substratum recognition and adhesion via homophilic (NCAM-NCAM), and heterophilic (NCAM-non-NCAM), interactions. NCAM is expressed as three major isoforms having different intracellular extensions. The extracellular portion of NCAM has five N-terminal Ig-like domains and two fibronectin type III domains. The double zipper adhesion complex model for NCAM homophilic binding involves Ig1, Ig2, and Ig3. By this model, Ig1 and Ig2 mediate dimerization of NCAM molecules situated on the same cell surface (cis interactions), and Ig3 domains mediate interactions between NCAM molecules expressed on the surface of opposing cells (trans interactions) through binding to the Ig1 and Ig2 domains. The adhesive ability of NCAM is modulated by the addition of polysialic acid chains to the fifth Ig-like domain.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061 131 PPS----KPTVNipSSATIGNRAVLTCsEQDGSPPSEYTWFKDGIVMPTnpkstrafSNSSYVLNPTTGELVFDPLSASD 206
Cdd:cd05730   1 PPTirarQSEVN--ATANLGQSVTLAC-DADGFPEPTMTWTKDGEPIES--------GEEKYSFNEDGSEMTILDVDKLD 69

                        90
                ....*....|...
gi 10720061 207 TGEYSCEARNGYG 219
Cdd:cd05730  70 EAEYTCIAENKAG 82

Fourth immunoglobulin (Ig)-like domain of hemolin, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain of hemolin and similar proteins. Hemolin, an insect immunoglobulin superfamily (IgSF) member containing four Ig-like domains, is a lipopolysaccharide-binding immune protein induced during bacterial infection. Hemolin shares significant sequence similarity with the first four Ig-like domains of the transmembrane cell adhesion molecules (CAMs) of the L1 family. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The fourth Ig-like domain of hemolin is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061  45 PVKLSCAYSGFSSPRVEWkfdqgdttrlvCYNNKITASYEDRVTFLPTGITFKSVTREDTGTYTCMVSEEGGNSYGEVKV 124
Cdd:cd20978  18 DVTLPCQVTGVPQPKITW-----------LHNGKPLQGPMERATVEDGTLTIINVQPEDTGYYGCVATNEIGDIYTETLL 86

                .
gi 10720061 125 K 125
Cdd:cd20978  87 H 87

Immunoglobulin C1-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 10720061   140 PSSATIGNRAVLTCSEQDGSPPS-EYTWFKDGIVMPTNPKST--RAFSNSSYVLnptTGELVFDPLSASDTGEYSC 212
Cdd:pfam07654   6 PSPEELGKPNTLTCLVTGFYPPDiTVTWLKNGQEVTEGVKTTppSPNSDWTYQL---SSYLTVTPSDWESGDEYTC 78

C-terminal immunoglobulin (Ig)-like domain of myotilin; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the C-terminal immunoglobulin (Ig)-like domain of myotilin. Mytolin belongs to the palladin-myotilin-myopalladin family. Proteins belonging to the latter family contain multiple Ig-like domains and function as scaffolds, modulating the actin cytoskeleton. Myotilin is most abundant in skeletal and cardiac muscle and is involved in maintaining sarcomere integrity. It binds to alpha-actinin, filamin, and actin. Mutations in myotilin lead to muscle disorders. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061  37 EVRIPENNPVKLSCAYSGFSSPRVEWKFDQgdttRLVCYNNKITASYED---RVTFLptgitFKSVTREDTGTYTCMVSE 113
Cdd:cd05892   9 NKKVLEGDPVRLECQISAIPPPQIFWKKNN----EMLQYNTDRISLYQDncgRICLL-----IQNANKKDAGWYTVSAVN 79

                ...
gi 10720061 114 EGG 116
Cdd:cd05892  80 EAG 82

Second immunoglobulin (Ig)-like domain of the nectin-like molecules Necl-1 - Necl-4; member of the I-set of Ig superfamily domains; The members here are composed of the second immunoglobulin (Ig)-like domain of the nectin-like molecules Necl-1 (also known as cell adhesion molecule 3 or CADM3), Necl-2 (also known as CADM1), Necl-3 (also known as CADM2) and Necl-4 (also known as CADM4). These nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 through Necl-5). These have an extracellular region containing three Ig-like domains, one transmembrane region, and one cytoplasmic region. The N-terminal Ig-like domain of the extracellular region belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-1 and Necl-2 have Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-1 is specifically expressed in neural tissue and is important to the formation of synapses, axon bundles, and myelinated axons. Necl-2 is expressed in a wide variety of tissues, and is a putative tumour suppressor gene, which is downregulated in aggressive neuroblastoma. Necl-3 has been shown to accumulate in tissues of the central and peripheral nervous system, where it is expressed in ependymal cells and myelinated axons. It is observed at the interface between the axon shaft and the myelin sheath. Necl-4 is expressed on Schwann cells, and plays a key part in initiating peripheral nervous system (PNS) myelination. Necl-4 participates in cell-cell adhesion and is proposed to play a role in tumor suppression.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|..
gi 10720061 129 LVPPSKPTVNIPSSATI-GNRAVLTCSEQDGSPPSEYTWFKD 169
Cdd:cd05761   1 LGVPEKPVITGFTSPVVeGDEITLTCTTSGSKPAADIRWFKN 42

Fourth immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin domain of the Drosophila melanogaster Down syndrome cell adhesion molecule (DSCAM) protein and similar proteins. Down syndrome cell adhesion molecule (DSCAM) is a cell adhesion molecule that plays critical roles in neural development, including axon guidance and branching, axon target recognition, self-avoidance and synaptic formation. DSCAM belongs to the immunoglobulin superfamily and contributes to defects in the central nervous system in Down syndrome patients. Vertebrate DSCAMs differ from Drosophila Dscam1 in that they lack the extensive alternative splicing that occurs in the insect gene. Drosophila melanogaster Dscam has 38,016 isoforms generated by the alternative splicing of four variable exon clusters, which allows every neuron in the fly to display a distinctive set of Dscam proteins on its cell surface. Drosophila Dscam1 is a cell-surface protein that plays important roles in neural development and axon tiling of neurons. It is shown that thousands of isoforms bind themselves through specific homophilic (self-binding) interactions, a process which mediates cellular self-recognition. Drosophila Dscam2 is also alternatively spliced and plays a key role in the development of two visual system neurons, monopolar cells L1 and L2. This group is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 10720061 146 GNRAVLTCSEQdGSPPSEYTWFKDGIVMPTNPKstraFSNSSYVLNptTGELV----FDPLSASDTGEYSCEARNGYGT 220
Cdd:cd20956  16 GPSVSLKCVAS-GNPLPQITWTLDGFPIPESPR----FRVGDYVTS--DGDVVsyvnISSVRVEDGGEYTCTATNDVGS 87

Immunoglobulin variable domain (IgV); The members here are composed of the immunoglobulin variable domain (IgV). The IgV family contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology, and are components of immunoglobulin (Ig) and T cell receptors. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. In Ig, each chain is composed of one variable domain (IgV) and one or more constant domains (IgC); these names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. Within the variable domain, there are regions of even more variability called the hypervariable or complementarity-determining regions (CDRs) which are responsible for antigen binding. A predominant feature of most Ig domains is the disulfide bridge connecting 2 beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E and, D strands in one sheet and A', G, F, C, C', and C" strands in the other.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 10720061  31 VHSSEPEVRIPENNPVKLSCAYSG-FSSPRVEW-------------KFDQGDTTRLVCYNNKITASYEDRVTFLptgITF 96
Cdd:cd00099   1 VTQSPRSLSVQEGESVTLSCEVSSsFSSTYIYWyrqkpgqgpefliYLSSSKGKTKGGVPGRFSGSRDGTSSFS---LTI 77

                        90       100
                ....*....|....*....|.
gi 10720061  97 KSVTREDTGTYTCMVSEEGGN 117
Cdd:cd00099  78 SNLQPEDSGTYYCAVSESGGT 98