Class I Histocompatibility antigen, domains alpha 1 and 2;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634  51 HTLRYNVRAHSLEGSEKTQLLVLIYVDEELFLKYNGDSR--ETEPLGCWIkGHGGNETCARETNNLLKVEEKLRGMMAEV 128
Cdd:pfam00129   3 HSLRYFYTAVSRPGLGEPRFIAVGYVDDTQFVRFDSDAAnpRMEPRAPWI-EQEGPEYWERETQIAKGNEQIFRENLRTL 81

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 129 INQKSQEE-GLHTLQATLGCELLSNG-STRGFWHLGYDGQNFLTFDQKTLTWTVDGPSTQQNKMFWKThAPRADLVKTFL 206
Cdd:pfam00129  82 LGYYNQSEgGSHTLQWMYGCDVGPDGrLLRGYEQFAYDGKDYIALNEDLRSWTAADPAAQITKRKWEA-AGEAERQRAYL 160

                         170
                  ....*....|..
gi 1039778634 207 DDICPAHLQRYL 218
Cdd:pfam00129 161 EGECVEWLRRYL 172

Class I Histocompatibility antigen, domains alpha 1 and 2;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634  51 HTLRYNVRAHSLEGSEKTQLLVLIYVDEELFLKYNGDSR--ETEPLGCWIkGHGGNETCARETNNLLKVEEKLRGMMAEV 128
Cdd:pfam00129   3 HSLRYFYTAVSRPGLGEPRFIAVGYVDDTQFVRFDSDAAnpRMEPRAPWI-EQEGPEYWERETQIAKGNEQIFRENLRTL 81

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 129 INQKSQEE-GLHTLQATLGCELLSNG-STRGFWHLGYDGQNFLTFDQKTLTWTVDGPSTQQNKMFWKThAPRADLVKTFL 206
Cdd:pfam00129  82 LGYYNQSEgGSHTLQWMYGCDVGPDGrLLRGYEQFAYDGKDYIALNEDLRSWTAADPAAQITKRKWEA-AGEAERQRAYL 160

                         170
                  ....*....|..
gi 1039778634 207 DDICPAHLQRYL 218
Cdd:pfam00129 161 EGECVEWLRRYL 172

Immunoglobulin C-Type;

                           10        20        30        40        50        60
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1039778634  245 VTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETiLPSGDGTYQARVSIRV---LPGQEPQFSCNLRH 310
Cdd:smart00407   2 ATLVCLVSGFYPPDITVTWLRNGQEVTEGVSTTDP-LKNSDGTYFLSSYLTVpasTWESGDVYTCQVTH 69

Class I Histocompatibility antigen, domains alpha 1 and 2;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634  51 HTLRYNVRAHSLEGSEKTQLLVLIYVDEELFLKYNGDSR--ETEPLGCWIkGHGGNETCARETNNLLKVEEKLRGMMAEV 128
Cdd:pfam00129   3 HSLRYFYTAVSRPGLGEPRFIAVGYVDDTQFVRFDSDAAnpRMEPRAPWI-EQEGPEYWERETQIAKGNEQIFRENLRTL 81

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 129 INQKSQEE-GLHTLQATLGCELLSNG-STRGFWHLGYDGQNFLTFDQKTLTWTVDGPSTQQNKMFWKThAPRADLVKTFL 206
Cdd:pfam00129  82 LGYYNQSEgGSHTLQWMYGCDVGPDGrLLRGYEQFAYDGKDYIALNEDLRSWTAADPAAQITKRKWEA-AGEAERQRAYL 160

                         170
                  ....*....|..
gi 1039778634 207 DDICPAHLQRYL 218
Cdd:pfam00129 161 EGECVEWLRRYL 172

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of MIC-A and MIC-B; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ia major histocompatibility complex (MHC) immunoglobulin domain of MIC-A and MIC-B. MIC-A and MIC-B are homologs that serve as stress-inducible antigens on epithelial and epithelially derived cells. Both serve as ligands for the widely expressed activating immunoreceptor NKG2D, a C-type lectin-like activating immunoreceptor. MIC-B is very similar in structure to MIC-A and likely interacts with NKG2D in an analogous manner. The interdomain flexibility observed in the MIC-A structures, a feature unique to MIC proteins among MHC class I proteins and homologs, is also displayed by MIC-B, with an interdomain relationship intermediate between the two examples of MIC-A structures. Mapping sequence variations onto the structures of MIC-A and MIC-B reveals patterns completely distinct from those displayed by classical MHC class I proteins, with a number of substitutions falling on positions likely to affect interactions with NKG2D, but with other positions lying distant from the NKG2D binding sites or buried within the core of the proteins. Members of the IgC family are components of immunoglobulin, T-cell receptors, CD1 cell surface glycoproteins, secretory glycoproteins A/C, and major histocompatibility complex (MHC) class I/II molecules. In immunoglobulins, each chain is composed of one variable domain (IgV) and one or more IgC domains. These names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. The IgV domain is responsible for antigen binding and the IgC domain is involved in oligomerization and molecular interactions.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 228 TGPPMVTVTCRNYPVGRVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETILPSGDGTYQARVSIRVLPGQEPQFSCN 307
Cdd:cd21017     2 TVPPMVNVTRSEASEGNITVTCRASGFYPWNITLSWRQDGVSLSHDTQQWGDVLPDGNGTYQTWVATRICQGEEQRFTCY 81

                  ....*..
gi 1039778634 308 LRH-GNH 313
Cdd:cd21017    82 MEHsGNH 88

Immunoglobulin domain of Zn-alpha2-glycoprotein (ZAG); member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin domain of Zn-alpha2-glycoprotein (ZAG). ZAG is a soluble protein that is present in serum and other body fluids. ZAG stimulates lipid degradation in adipocytes and causes the extensive fat losses associated with some advanced cancers. The 2.8 angstrom crystal structure of ZAG resembles a class I major histocompatibility complex (MHC) heavy chain, but ZAG does not bind the class I light chain beta-2-microglobulin. The ZAG structure includes a large groove analogous to class I MHC peptide binding grooves. Instead of a peptide, the ZAG groove contains a nonpeptidic compound that may be implicated in lipid catabolism under normal or pathological conditions. IgC_MHC_I_alpha3; Immunoglobulin (Ig) domain of major histocompatibility complex (MHC) class I alpha chain. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 226 QDtgPPMVTVTCRNYPVGRVTLTCRAFNLYTREATLVWLQDGKPvqQKTFRSETILPSGDGTYQARVSIRVLPGQEPQFS 305
Cdd:cd21010     2 QD--PPSVSVTSHVAPGKNRTLKCLAYDFYPRGISLHWTRAGKV--QESESGGDVLPSGNGTYQSWVVVEVPPQDRAPYS 77

                  ....*.
gi 1039778634 306 CNLRHG 311
Cdd:cd21010    78 CHVEHS 83

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of H2-Dd; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ia major histocompatibility complex (MHC) immunoglobulin domain of H2-Dd. Mouse MHC is composed of 11 subclasses. It includes the classical MHC class I (MHC-Ia) that comprises H-2D, H-2K and H-2L subclasses, the non-classical MHC class I (MHCIb) that comprises H-2Q, H-2M and H-2T subclasses, the classical MHC class II (MHC-IIa) that includes H-2A(I-A) and H-2E(I-E) subclasses, and the non-classical MHC class II (MHC-IIb) comprises H-2M and H-2O. H-2K, H-2D, and H-2L are 80 to 90% homologous at the amino acid level yet appear to be involved in different recognition reactions and are differentially expressed on lymphoid cells. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 228 TGPPMVTVTCRNYPVGRVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETiLPSGDGTYQARVSIRVLPGQEPQFSCN 307
Cdd:cd21020     3 TDPPKAHVTHHRRPEGDVTLRCWALGFYPADITLTWQLNGEELTQEMELVET-RPAGDGTFQKWASVVVPLGKEQKYTCH 81

                  ...
gi 1039778634 308 LRH 310
Cdd:cd21020    82 VEH 84

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of RT1-Aa; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ia major histocompatibility complex (MHC) immunoglobulin domain of RT1-Aa. While most mammalian species transport these peptides into the ER via a single allele of TAP, rats have evolved different TAPs, TAP-A and TAP-B, RT1-Aa and RT1-A1c, which are associated with TAP-A and TAP-B. The rat MHC class Ia molecule RT1-Aa has the unusual capacity to bind long peptides ending in arginine, such as MTF-E, a thirteen-residue, maternally transmitted minor histocompatibility antigen. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 228 TGPPMVTVTCRNYPVGRVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETiLPSGDGTYQARVSIRVLPGQEPQFSCN 307
Cdd:cd21015     2 SDPPEAHVTLHPRPEGDVTLRCWALGFYPADITLTWQLNGEDLTQDMELVET-RPAGDGTFQKWASVVVPLGKEQNYTCR 80

                  ...
gi 1039778634 308 LRH 310
Cdd:cd21015    81 VEH 83

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) E; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) E. HLA-E is the first human class Ib major histocompatibility complex molecule to be crystallized. Like other MHC class I molecules, HLA-E is a heterodimer consisting of an a heavy chain and light chain beta-2-microglobulin. HLA-E is highly conserved and almost nonpolymorphic, and has recently been shown to be the first specialized ligand for natural killer cell receptors. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 230 PPMVTVTcrNYPVG--RVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETiLPSGDGTYQARVSIRVLPGQEPQFSCN 307
Cdd:cd21024     5 PPKTHVT--HHPISdhEATLRCWALGFYPAEITLTWQQDGEGHTQDTELVET-RPAGDGTFQKWAAVVVPSGEEQRYTCH 81

                  ...
gi 1039778634 308 LRH 310
Cdd:cd21024    82 VQH 84

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of Qa-2; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of QA-2. Qa-2 is a nonclassical MHC Ib antigen, which has been implicated in both innate and adaptive immune responses, as well as embryonic development. Qa-2 has an unusual peptide binding specificity in that it requires two dominant C-terminal anchor residues and is capable of associating with a substantially more diverse array of peptide sequences than other nonclassical MHC. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 228 TGPPMVTVTCRNYPVGRVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETiLPSGDGTYQARVSIRVLPGQEPQFSCN 307
Cdd:cd21014     2 TDPPKAHVTHHPRSYGAVTLRCWALGFYPADITLTWQLNGEELTQDMELVET-RPAGDGTFQKWASVVVPLGKEQNYTCH 80

                  ...
gi 1039778634 308 LRH 310
Cdd:cd21014    81 VNH 83

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) A; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the class Ia major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) A. The classical class I molecules (HLA-A, -B, and -C) are responsible for the presentation of endogenous antigen to CD8+ T cells. The receptor is a heterodimer, and is composed of a heavy alpha chain and smaller beta chain. The alpha chain is encoded by a variant HLA-A gene, and the beta chain (beta-2-microglobulin) is an invariant beta-2-microglobulin molecule. The beta-2-microglobulin protein is coded for by a separate region of the human genome. HLA-A2 is associated with spontaneous abortions, HIV, and Hodgkin lymphoma. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 226 QDTGPPMVTVTCRNYPVGRVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETiLPSGDGTYQARVSIRVLPGQEPQFS 305
Cdd:cd21027     1 QRTDAPKTHMTHHAVSDHEATLRCWALSFYPAEITLTWQRDGEDQTQDTELVET-RPAGDGTFQKWAAVVVPSGQEQRYT 79

                  ....*
gi 1039778634 306 CNLRH 310
Cdd:cd21027    80 CHVQH 84

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of Qa-1 and similar proteins; member of the C1-set of Ig superfamily (IgSF) domains; Class Ib major histocompatibility complex (MHC) immunoglobulin domain of Qa-1 and similar proteins. Qa-1 presents hydrophobic peptides including Qdm derived from the leader sequence of classical MHC I molecules for immune surveillance by NK cells. Qa-1 bound peptides derived from the TCR Vbeta8.2 of activated T cells also activates CD8+ regulatory T cells to control autoimmunity and maintain self-tolerance. Four allotypes of Qa-1 (Qa-1a-d) are expressed that are highly conserved in sequence but have several variations that could affect peptide binding to Qa-1 or TCR recognition. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 230 PPMVTVTCRNYPVGRVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETiLPSGDGTYQARVSIRVLPGQEPQFSCNLR 309
Cdd:cd21013     4 PPKAHVTHHPRSEGYVTLRCWALGFYPADITLTWQLNGEELTQDMEFVET-RPAGDGTFQKWASVVVPLGKEQKYTCHVE 82

                  .
gi 1039778634 310 H 310
Cdd:cd21013    83 H 83

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) G; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) G. HLA-G histocompatibility antigen (also known as human leukocyte antigen G ; HLA-G) is a protein that in humans is encoded by the HLA-G gene. HLA-G belongs to the HLA nonclassical class I heavy chain paralogs. This class I molecule is a heterodimer consisting of a heavy chain and light chain, beta-2-microglobulin. The heavy chain is anchored in the membrane. HLA-G may play a role in immune tolerance in pregnancy, being expressed in the placenta by extravillous trophoblast cells (EVT), while the classical MHC class I genes (HLA-A and HLA-B) are not. Immunoglobulin (Ig) domain of major histocompatibility complex (MHC) class I and class II. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells. MHC class II molecules play a key role in the initiation of the antigen-specific immune repose. These molecules have been shown to be expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice. The expression of these molecules has been shown to be induced in nonprofessional APCs such as keratinocyctes, and they are expressed on the surface of activated human T cells and on T cells from other species. The MHC II molecules present antigenic peptides to CD4(+) T-lymphocytes. These peptides derive mostly from proteolytic processing via the endocytic pathway, of antigens internalized by the APC. These peptides bind to the MHC class II molecules in the endosome before they are transported to the cell surface. MHC class II molecules are heterodimers, comprised of two similarly-sized membrane-spanning chains, alpha and beta. Each chain had two globular domains (N- and C-terminal), and a membrane-anchoring transmembrane segment. The two chains form a compact four-domain structure. The peptide-binding site is a cleft in the structure.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 227 DTGPPMVTVTcrNYPV--GRVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETiLPSGDGTYQARVSIRVLPGQEPQF 304
Cdd:cd21022     1 RADPPKTHVT--HHPVfdYEATLRCWALGFYPAEIILTWQRDGEDQTQDVELVET-RPAGDGTFQKWAAVVVPSGEEQRY 77

                  ....*.
gi 1039778634 305 SCNLRH 310
Cdd:cd21022    78 TCHVQH 83

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of HLA-Cw3 and HLA-Cw4; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of HLA-Cw3 and HLA-Cw4. HLA-C belongs to the MHC class I heavy chain receptors. The C receptor is a heterodimer consisting of a HLA-C mature gene product and beta-2-microglobulin. The mature C chain is anchored in the membrane. MHC Class I molecules, like HLA-C, are expressed in nearly all cells, and present small peptides to the immune system which surveys for non-self peptides. HLA-C is a locus on chromosome 6, which encodes for a large number of HLA-C alleles that are Class-I MHC receptors. Class Ib histocompatibility leukocyte antigens (HLA)-Cw3 and (HLA)-Cw4 are ligands for the natural killer (NK) cell inhibitory receptors KIR2DL2 and KIR2DL1, respectively. HLA-Cw3 and related alleles (HLA-Cw1, -Cw7, and -Cw8) contain Ser77 and Asn80 and interact with KIR that are reactive with the GL183 antibody Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. HLA-Cw4 and related alleles (HLA-Cw2, -Cw5, and -Cw6) have Asn77 and Lys80 and are recognized by KIR reactive with the EB6 15 or HP-3E4 16 antibody. Members of the IgC family are components of immunoglobulin, T-cell receptors, CD1 cell surface glycoproteins, secretory glycoproteins A/C, and major histocompatibility complex (MHC) class I/II molecules. In immunoglobulins, each chain is composed of one variable domain (IgV) and one or more IgC domains. These names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. The IgV domain is responsible for antigen binding, and the IgC domain is involved in oligomerization and molecular interactions.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 231 PMVTVTcrNYPVG--RVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETiLPSGDGTYQARVSIRVLPGQEPQFSCNL 308
Cdd:cd21025     6 PKTHVT--HHPVSdhEATLRCWALGFYPAEITLTWQWDGEDQTQDTELVET-RPAGDGTFQKWAAVVVPSGEEQRYTCHV 82

                  ..
gi 1039778634 309 RH 310
Cdd:cd21025    83 QH 84

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of Qa-1b; member of the C1-set of Ig superfamily (IgSF) domains; The non-classical mouse MHC class I (MHC-I) molecule Qa-1b is a non-polymorphic MHC molecule with an important function in innate immunity. It binds and presents signal peptides of classical MHC-I molecules at the cell surface and, as such, act as an indirect sensor for the normal expression of MHC-I molecules. This signal peptide dominantly accommodated in the groove of Qa-1b is called Qdm, for Qa-1 determinant modifier, and its amino acid sequence AMAPRTLLL is highly conserved among mammalian species. The Qdm/Qa-1b complex serves as a ligand for the germ-line encoded heterodimeric CD94/NKG2A receptors expressed on natural killer (NK) cells and activated CD8+ T cells and transduces inhibitory signals to these lymphocytes. Thus, upon binding, Qa-1b signals NK cells not to engage in cell lysis. The molecular basis of Qa-1b function is unclear.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 226 QDTGPPMVTVTCRNYPVGRVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETiLPSGDGTYQARVSIRVLPGQEPQFS 305
Cdd:cd21820     1 QRSDPPKAHVTHHPRSEDEVTLRCWALGFYPADITLTWQLNGEELTQDMELVET-RPAGDGTFQKWAAVVVPLGKEQYYT 79

                  ....*
gi 1039778634 306 CNLRH 310
Cdd:cd21820    80 CHVYH 84

CH3 domain (third constant Ig domain of the heavy chain) in immunoglobulin heavy alpha, gamma, and delta chains, and CH4 domain (fourth constant Ig domain of the heavy chain) in immunoglobulin heavy alpha, epsilon, and mu chains; member of the C1-set of I; The members here are composed of the third and fourth immunoglobulin constant domain (IgC) of alpha, delta, gamma and alpha, epsilon, and mu heavy chains, respectively. This domain is found on the Fc fragment. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. There are two types of light chains: kappa and lambda; each is composed of a constant domain and a variable domain. There are five types of heavy chains: alpha, delta, epsilon, gamma, and mu, all consisting of a variable domain (VH) with three (alpha, delta and gamma) or four (epsilon and mu) constant domains (CH1 to CH4). Ig molecules are modular proteins, in which the variable and constant domains have clear, conserved sequence patterns.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 1039778634 244 RVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETILPSGDGTYQArVSIRVLPGQEPQ----FSCNLRH 310
Cdd:cd05768    18 TVTLTCLVKGFYPEDIFVSWLQNGEPLPSADYKTTAPVPESDGSFFV-YSKLNVSTADWNsgdvFSCVVGH 87

MHC-I family domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039778634 141 LQATLGCELLSNGSTRGFWHLGYDGQNFLTFdQKTLTWTV-DGPSTQQN--KMFWKTHAPRaDLVKTFLDDICPahlqRY 217
Cdd:pfam16497  96 IQISAGCELHPGNASVSFLRVAYQGSDLLSF-QGTSWLPSpKGPSRAQLvcKVLNQDQGTK-ETVQWLLSDTCP----RF 169

                  ....
gi 1039778634 218 LASL 221
Cdd:pfam16497 170 VLGL 173

CH2 domain (second constant Ig domain of the heavy chain) in immunoglobulin mu chain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin constant domain (IgC) of mu heavy chains. This domain is found on the Fc fragment. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. There are two types of light chains: kappa and lambda; each is composed of a constant domain and a variable domain. There are five types of heavy chains: alpha, delta, epsilon, gamma, and mu, all consisting of a variable domain (VH) with three (alpha, delta and gamma) or four (epsilon and mu) constant domains (CH1 to CH4). Ig molecules are modular proteins, in which the variable and constant domains have clear, conserved sequence patterns.

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gi 1039778634 245 VTLTCRAFNLYTREATLVWLQDGKPVQQKT-FRSETILPSGDGTYQARVSIRVLPGQ---EPQFSCNLRHGNHSIMQTA 319
Cdd:cd16093    20 ATFVCLATGFSPKTISFKWLRNGKEVTSSTgAVVEEPKEDGKTLYSATSFLTITESEwksQTEFTCEFKHKGEIVEKNA 98

Immunoglobulin light chain Constant domain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) light chain constant (C) domain. 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. There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determine the type of immunoglobulin: IgA, IgG, IgD, IgE, and IgM, respectively. In higher vertebrates, there are two types of light chain, designated kappa and lambda, which seem to be functionally identical, and can associate with any of the heavy chains.

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gi 1039778634 230 PPMVTVTC---RNYPVGRVTLTCRAFNLYTREATLVWLQDGKPVQQKTFRSETILPSgDGTYQA 290
Cdd:cd07699     1 APSVTIFPpssEELSSGKATLVCLINKFYPGFATVTWKVDGSTVSSGVTTSKTEQQS-DNTYSM 63

Class II major histocompatibility complex (MHC) alpha chain immunoglobulin domain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) domain of the major histocompatibility complex (MHC) class II alpha chain. MHC class II molecules play a key role in the initiation of the antigen-specific immune reponse. These molecules have been shown to be expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice. The expression of these molecules has been shown to be induced in nonprofessional APCs such as keratinocyctes, and they are also expressed on the surface of activated human T cells and on T cells from other species. The MHC II molecules present antigenic peptides to CD4(+) T-lymphocytes. These peptides derive mostly from proteolytic processing via the endocytic pathway, of antigens internalized by the APC. These peptides bind to the MHC class II molecules in the endosome before they are transported to the cell surface. MHC class II molecules are heterodimers, comprised of two similarly-sized membrane-spanning chains, alpha and beta. Each chain had two globular domains (N- and C-terminal), and a membrane-anchoring transmembrane segment. The two chains form a compact four-domain structure. The peptide-binding site is a cleft in the structure.

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gi 1039778634 229 GPPMVTVtcrnYPVGRV------TLTCRAFNLYTREATLVWLQDGKPVQQKTfrSETI-LPSGDGTYQARVSIRVLPGQE 301
Cdd:cd05767     1 VPPEVTV----FPKSPVelgepnTLICFVDNFFPPVINVTWLRNGQPVTDGV--SETVfLPREDHSFRKFSYLPFTPSEG 74

                          90
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gi 1039778634 302 PQFSCNLRHG 311
Cdd:cd05767    75 DIYDCRVEHW 84