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        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768006397 283 PQVVPSSLNLVENARSVDLTCQTVNQSVNVQWFLSGQPLLPSEHLQLSADNRTLIIHGLQRNDTGPYACEVWNWGSRARS 362
Cdd:cd05740    2 PFISSNNSNPVEDKDAVTLTCEPETQNTSYLWWFNGQSLPVTPRLTLSNGNRTLTLLNVTREDAGAYQCEISNPVSANRS 81

                 ....*...
gi 768006397 363 EPLELTIN 370
Cdd:cd05740   82 DPVTLDVI 89

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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 768006397 396 SSLTLQCWAESKPGAEYRWTLEhSTGEHLGEQLIIRALTWEHDGIYNCTASNSLTGLARSTSVLVKV 462
Cdd:cd20948   11 ENLNLSCHAASNPPAQYSWTIN-GTFQTSSQELFLPAITENNEGTYTCSAHNSLTGKNISLVLSVTV 76

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 768006397 283 PQVVPSSLNLVENARSVDLTCQTVNQSVNVQWFLSGQPLLPSEHLQLSADNRTLIIHGLQRNDTGPYACEVWNWGSRARS 362
Cdd:cd05740    2 PFISSNNSNPVEDKDAVTLTCEPETQNTSYLWWFNGQSLPVTPRLTLSNGNRTLTLLNVTREDAGAYQCEISNPVSANRS 81

                 ....*...
gi 768006397 363 EPLELTIN 370
Cdd:cd05740   82 DPVTLDVI 89

Fifth immunoglobulin (Ig)-like domain of the carcinoembryonic antigen (CEA) related cell adhesion molecule 5 (CEACAM5) and similar domains; member of the C2-set IgSF domains; The members here are composed of the fifth immunoglobulin (Ig)-like domain of the carcinoembryonic antigen (CEA) related cell adhesion molecule 5 (CEACAM5) and similar domains. 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. Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5), also known as CD66e (Cluster of Differentiation 66e), is a cell surface glycoprotein that plays a role in cell adhesion, intracellular signaling and tumor progression. Diseases associated with CEACAM5 include lung cancer and rectum cancer. 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. This group belongs to the C2-set of IgSF domains, having A, B, and E strands in one beta-sheet and A', G, F, C' in the other. Unlike other Ig domain sets, the C2-set lacks the D strand.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 768006397 396 SSLTLQCWAESKPGAEYRWTLEhSTGEHLGEQLIIRALTWEHDGIYNCTASNSLTGLARSTSVLVKV 462
Cdd:cd20948   11 ENLNLSCHAASNPPAQYSWTIN-GTFQTSSQELFLPAITENNEGTYTCSAHNSLTGKNISLVLSVTV 76

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

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 768006397    97 PSIAVSPGtaieqkDMVTFYCTTK-DVNITIHWVSNNLSIVFH-ERMQLSKDGKILTILI--VQREDSGTYQCEARDA 170
Cdd:smart00410   2 PSVTVKEG------ESVTLSCEASgSPPPEVTWYKQGGKLLAEsGRFSVSRSGSTSTLTIsnVTPEDSGTYTCAATNS 73

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768006397   202 EVVEVMEGSSMTFLAETKSHPPCAYTWFLLDSIL-----------SHTTRTFTIHAVSREHEGLYRCLVSNSATHLSSLG 270
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPPPEVTWYKQGGKLlaesgrfsvsrSGSTSTLTISNVTPEDSGTYTCAATNSSGSASSGT 81

                   ....
gi 768006397   271 TLKV 274
Cdd:smart00410  82 TLTV 85

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 768006397  198 VASGEVVEVMEGSSMTFLAETKSHPPCAYTWFLLDSILSH----------TTRTFTIHAVSREHEGLYRCLVSN 261
Cdd:pfam13927   5 TVSPSSVTVREGETVTLTCEATGSPPPTITWYKNGEPISSgstrsrslsgSNSTLTISNVTRSDAGTYTCVASN 78

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

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 768006397   298 SVDLTCQ-TVNQSVNVQWFLSG-QPLLPSEHLQLSADNR--TLIIHGLQRNDTGPYACEVWNwGSRARSEPLELTI 369
Cdd:smart00410  11 SVTLSCEaSGSPPPEVTWYKQGgKLLAESGRFSVSRSGStsTLTISNVTPEDSGTYTCAATN-SSGSASSGTTLTV 85

IL-1 receptor-like protein; Provisional

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768006397 244 IHAVSREHEGLYRCLVSNSatHLSSLGTLKVRVLETLTMPQVvpsslnlvENARSVDLTC------QTVNQSVNVQWFLS 317
Cdd:PHA02826 102 IGNVINIDEGIYICTISSG--NICEESTIRLTFDSGTINYQF--------NSGKDSKLHCygtdgiSSTFKDYTLTWYKN 171

                         90       100       110       120       130       140
                 ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 768006397 318 GQPLLPSEHLQLSADNRTLIIHGLQRNDTGPYACevwnwgsrarseplELTINYGPDQVHITRE 381
Cdd:PHA02826 172 GNIVLYTDRIQLRNNNSTLVIKSATHDDSGIYTC--------------NLRFNKNSNNYNITKE 221

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 768006397 283 PQVVPSSLNLVENARSVDLTCQTVNQSVNVQWFLSGQPLLPSEHLQLSADNRTLIIHGLQRNDTGPYACEVWNWGSRARS 362
Cdd:cd05740    2 PFISSNNSNPVEDKDAVTLTCEPETQNTSYLWWFNGQSLPVTPRLTLSNGNRTLTLLNVTREDAGAYQCEISNPVSANRS 81

                 ....*...
gi 768006397 363 EPLELTIN 370
Cdd:cd05740   82 DPVTLDVI 89

Fifth immunoglobulin (Ig)-like domain of the carcinoembryonic antigen (CEA) related cell adhesion molecule 5 (CEACAM5) and similar domains; member of the C2-set IgSF domains; The members here are composed of the fifth immunoglobulin (Ig)-like domain of the carcinoembryonic antigen (CEA) related cell adhesion molecule 5 (CEACAM5) and similar domains. 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. Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5), also known as CD66e (Cluster of Differentiation 66e), is a cell surface glycoprotein that plays a role in cell adhesion, intracellular signaling and tumor progression. Diseases associated with CEACAM5 include lung cancer and rectum cancer. 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. This group belongs to the C2-set of IgSF domains, having A, B, and E strands in one beta-sheet and A', G, F, C' in the other. Unlike other Ig domain sets, the C2-set lacks the D strand.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 768006397 396 SSLTLQCWAESKPGAEYRWTLEhSTGEHLGEQLIIRALTWEHDGIYNCTASNSLTGLARSTSVLVKV 462
Cdd:cd20948   11 ENLNLSCHAASNPPAQYSWTIN-GTFQTSSQELFLPAITENNEGTYTCSAHNSLTGKNISLVLSVTV 76

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

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 768006397    97 PSIAVSPGtaieqkDMVTFYCTTK-DVNITIHWVSNNLSIVFH-ERMQLSKDGKILTILI--VQREDSGTYQCEARDA 170
Cdd:smart00410   2 PSVTVKEG------ESVTLSCEASgSPPPEVTWYKQGGKLLAEsGRFSVSRSGSTSTLTIsnVTPEDSGTYTCAATNS 73

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768006397   202 EVVEVMEGSSMTFLAETKSHPPCAYTWFLLDSIL-----------SHTTRTFTIHAVSREHEGLYRCLVSNSATHLSSLG 270
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPPPEVTWYKQGGKLlaesgrfsvsrSGSTSTLTISNVTPEDSGTYTCAATNSSGSASSGT 81

                   ....
gi 768006397   271 TLKV 274
Cdd:smart00410  82 TLTV 85

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 768006397  298 SVDLTCQTVNQSV-NVQWFLSGQPLLPSEHLQLSADNR--TLIIHGLQRNDTGPYACEVWNWGSRARSEpLELTI 369
Cdd:pfam07679  17 SARFTCTVTGTPDpEVSWFKDGQPLRSSDRFKVTYEGGtyTLTISNVQPDDSGKYTCVATNSAGEAEAS-AELTV 90

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768006397  388 STIEAELNSSLTLQCWAESKPGAEYRWT--------LEHSTGEHLGEQ--LIIRALTWEHDGIYNCTASN 447
Cdd:pfam13927   9 SSVTVREGETVTLTCEATGSPPPTITWYkngepissGSTRSRSLSGSNstLTISNVTRSDAGTYTCVASN 78

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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 768006397 299 VDLTCQTV-NQSVNVQWFLSGQPLLPSEHL--QLSADNRTLIIHGLQRNDTGPYACEVWNWGSRARS 362
Cdd:cd00096    1 VTLTCSASgNPPPTITWYKNGKPLPPSSRDsrRSELGNGTLTISNVTLEDSGTYTCVASNSAGGSAS 67

Immunoglobulin domain; This domain contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768006397   96 KPSIAVSPgTAIEQKDMVTFYCTTK-DVNITIHWVSNNLSIvfhermqlsKDGKILTILIVQREDSGTYQCEARDALLSQ 174
Cdd:pfam13895   1 KPVLTPSP-TVVTEGEPVTLTCSAPgNPPPSYTWYKDGSAI---------SSSPNFFTLSVSAEDSGTYTCVARNGRGGK 70

                  ....*....
gi 768006397  175 RSDPIFLDV 183
Cdd:pfam13895  71 VSNPVELTV 79

Immunoglobulin domain; This domain contains immunoglobulin-like domains.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 768006397  396 SSLTLQCWAESKPGAEYRWTLEhstGEHLGEQ--LIIRALTWEHDGIYNCTASNSLTGLaRSTSVLVKV 462
Cdd:pfam13895  15 EPVTLTCSAPGNPPPSYTWYKD---GSAISSSpnFFTLSVSAEDSGTYTCVARNGRGGK-VSNPVELTV 79

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
                 ....*....|....*....|....*....|....*....|....*.
gi 768006397 311 NVQWFLSGQPLlPSEHLQLSADNRTLIIHGLQRN-DTGPYACEVWN 355
Cdd:cd20958   31 SITWEKDGRRL-PLNHRQRVFPNGTLVIENVQRSsDEGEYTCTARN 75

agrin-responsive first immunoglobulin-like domains (Ig1) of the MuSK ectodomain; a member of the I-set of IgSF domains; The members here are composed of the first immunoglobulin-like domains (Ig1) of the Muscle-specific kinase (MuSK). MuSK is a receptor tyrosine kinase specifically expressed in skeletal muscle, where it plays a central role in the formation and maintenance of the neuromuscular junction (NMJ). MuSK is activated by agrin, a neuron-derived heparan sulfate proteoglycan. The activation of MUSK in myotubes regulates the formation of NMJs through the regulation of different processes including the specific expression of genes in subsynaptic nuclei, the reorganization of the actin cytoskeleton and the clustering of the acetylcholine receptors (AChR) in the postsynaptic membrane. 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 the MuSK lacks this strand and thus it 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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 768006397 382 SASEMISTIEAELNSSLTLQCWAESKPGAEYRWT------LEHSTGEHL---GEQLIIRALTWEHDGIYNCTASNSLTG 451
Cdd:cd20970    4 STPQPSFTVTAREGENATFMCRAEGSPEPEISWTrngnliIEFNTRYIVrenGTTLTIRNIRRSDMGIYLCIASNGVPG 82

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 768006397   98 SIAVSPGTAieqkdmVTFYCTTK-DVNITIHWVSNNLSIVFHERMQLSKDGKI--LTILIVQREDSGTYQCEA 167
Cdd:pfam07679   9 DVEVQEGES------ARFTCTVTgTPDPEVSWFKDGQPLRSSDRFKVTYEGGTytLTISNVQPDDSGKYTCVA 75

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
                 ....*....|....*....|....*....|....*....|....*....|...
gi 768006397 226 YTWFLLDSILSHTTR----------TFTIHAVSREHEGLYRCLVSNSATHLSS 268
Cdd:cd00096   15 ITWYKNGKPLPPSSRdsrrselgngTLTISNVTLEDSGTYTCVASNSAGGSAS 67

Immunoglobulin domain; This domain contains immunoglobulin-like domains.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 768006397  202 EVVEVMEGSSMTFLAETKSHPPCAYTWFLLDSILShTTRTFTIHAVSREHEGLYRCLVSNSATHLSS 268
Cdd:pfam13895   7 SPTVVTEGEPVTLTCSAPGNPPPSYTWYKDGSAIS-SSPNFFTLSVSAEDSGTYTCVARNGRGGKVS 72

Immunoglobulin (Ig)-like domain found in Leukocyte Ig-like receptors, Natural killer inhibitory receptors (KIRs) and similar domains; member of Immunoglobulin Constant-2 set of IgSF domains; The members here are composed of the first and second immunoglobulin (Ig)-like domains found in Leukocyte Ig-like receptors (LILRs), Natural killer inhibitory receptors (KIRs, also known as also known as cluster of differentiation (CD) 158), and similar proteins. This group includes LILRB1 (also known as LIR-1), LILRA5 (also known as LIR9), an activating natural cytotoxicity receptor NKp46, the immune-type receptor glycoprotein VI (GPVI), and the IgA-specific receptor Fc-alphaRI (also known as cluster of differentiation (CD) 89). LILRs are a family of immunoreceptors expressed on expressed on T and B cells, on monocytes, dendritic cells, and subgroups of natural killer (NK) cells. The human LILR family contains nine proteins (LILRA1-3, and 5, and LILRB1-5). From functional assays, and as the cytoplasmic domains of various LILRs, for example LILRB1, LILRB2 (also known as LIR-2), and LILRB3 (also known as LIR-3) contain immunoreceptor tyrosine-based inhibitory motifs (ITIMs), it is thought that LIR proteins are inhibitory receptors. Of the eight LIR family proteins, only LILRB1, and LILRB2, show detectable binding to class I MHC molecules; ligands for the other members have yet to be determined. The extracellular portions of the different LIR proteins contain different numbers of Ig-like domains for example, four in the case of LILRB1, and LILRB2, and two in the case of LILRB4 (also known as LIR-5). The activating natural cytotoxicity receptor NKp46 is expressed in natural killer cells, and is organized as an extracellular portion having two Ig-like extracellular domains, a transmembrane domain, and a small cytoplasmic portion. GPVI, which also contains two Ig-like domains, participates in the processes of collagen-mediated platelet activation and arterial thrombus formation. Fc-alphaRI is expressed on monocytes, eosinophils, neutrophils, and macrophages; it mediates IgA-induced immune effector responses such as phagocytosis, antibody-dependent cell-mediated cytotoxicity and respiratory burst. Killer cell immunoglobulin-like receptors (KIRs; also known as CD158 for human KIR) are transmembrane glycoproteins expressed by natural killer cells and subsets of T cells. KIRs are a family of highly polymorphic activating and inhibitory receptors that serve as key regulators of human NK cell function. The KIR proteins are classified by the number of extracellular immunoglobulin domains (2D or 3D) and by whether they have a long (L) or short (S) cytoplasmic domain. KIR proteins with the long cytoplasmic domain transduce inhibitory signals upon ligand binding via an immune tyrosine-based inhibitory motif (ITIM), while KIR proteins with the short cytoplasmic domain lack the ITIM motif and instead associate with the TYRO protein tyrosine kinase binding protein to transduce activating signals. The major ligands for KIR are MHC class I (HLA-A, -B or -C) molecules.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768006397 284 QVVPSSLnlVENARSVDLTCQTVNQSVNVQWFLSGQPllPSEHLQLSADNRT---LIIHGLQRNDTGPYACEVWNWGSRA 360
Cdd:cd16843    5 SAEPSSV--VPLGENVTIRCQGPPEAVLFQLYKEGNS--LSQGTVREKEPQNkaeFYIPHMDRNHAGRYRCRYRSGTLWS 80

                         90
                 ....*....|
gi 768006397 361 R-SEPLELTI 369
Cdd:cd16843   81 EpSDPLELVV 90

IL-1 receptor-like protein; Provisional

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768006397 244 IHAVSREHEGLYRCLVSNSatHLSSLGTLKVRVLETLTMPQVvpsslnlvENARSVDLTC------QTVNQSVNVQWFLS 317
Cdd:PHA02826 102 IGNVINIDEGIYICTISSG--NICEESTIRLTFDSGTINYQF--------NSGKDSKLHCygtdgiSSTFKDYTLTWYKN 171

                         90       100       110       120       130       140
                 ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 768006397 318 GQPLLPSEHLQLSADNRTLIIHGLQRNDTGPYACevwnwgsrarseplELTINYGPDQVHITRE 381
Cdd:PHA02826 172 GNIVLYTDRIQLRNNNSTLVIKSATHDDSGIYTC--------------NLRFNKNSNNYNITKE 221

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 768006397  388 STIEAELNSSLTLQCWA-ESKPGAEYRWTLE-----------HSTGEHLGEQLIIRALTWEHDGIYNCTASNSLTGLARS 455
Cdd:pfam00047   4 PTVTVLEGDSATLTCSAsTGSPGPDVTWSKEggtlieslkvkHDNGRTTQSSLLISNVTKEDAGTYTCVVNNPGGSATLS 83

                  ...
gi 768006397  456 TSV 458
Cdd:pfam00047  84 TSL 86

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 768006397  97 PSIAVSPGtaieqkDMVTFYCTTKDVNIT--IHW-----------------VSNNLSIVFHERMQLSKDGK---ILTILI 154
Cdd:cd00099    6 RSLSVQEG------ESVTLSCEVSSSFSStyIYWyrqkpgqgpefliylssSKGKTKGGVPGRFSGSRDGTssfSLTISN 79

                         90
                 ....*....|....*.
gi 768006397 155 VQREDSGTYQCEARDA 170
Cdd:cd00099   80 LQPEDSGTYYCAVSES 95

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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 768006397  97 PSIAVSPGTAIEQKDM--VTFYCT-TKDVNITIHWVSNnlSIVFHERMQLSKDGK-ILTILIVQREDSGTYQCEA 167
Cdd:cd20978    1 PKFIQKPEKNVVVKGGqdVTLPCQvTGVPQPKITWLHN--GKPLQGPMERATVEDgTLTIINVQPEDTGYYGCVA 73