Class I major histocompatibility complex (MHC) homolog m144; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) domain of major histocompatibility complex (MHC) homolog m144 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 61660253 163 AVSPQLEVERRSSGREGGMRLRCFARDYYPADLEIRWWKDDGGGGALPQTSKQHHDPLPSGNGLYQKHIDVYVDGGLEHV 242
Cdd:cd21028   1 AVSPQLEVERRSSGREGGMRLRCFARDYYPADLEIRWWKDDGGGGALPQTSKQHHDPLPSGNGLYQKHIDVYVDGGLEHV 80

                        90       100
                ....*....|....*....|.
gi 61660253 243 YSCRVKGIATGLELQIVRWKG 263
Cdd:cd21028  81 YSCRVKGIATGLELQIVRWKG 101

Class I major histocompatibility complex (MHC) homolog m144; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) domain of major histocompatibility complex (MHC) homolog m144 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 61660253 163 AVSPQLEVERRSSGREGGMRLRCFARDYYPADLEIRWWKDDGGGGALPQTSKQHHDPLPSGNGLYQKHIDVYVDGGLEHV 242
Cdd:cd21028   1 AVSPQLEVERRSSGREGGMRLRCFARDYYPADLEIRWWKDDGGGGALPQTSKQHHDPLPSGNGLYQKHIDVYVDGGLEHV 80

                        90       100
                ....*....|....*....|.
gi 61660253 243 YSCRVKGIATGLELQIVRWKG 263
Cdd:cd21028  81 YSCRVKGIATGLELQIVRWKG 101

Immunoglobulin C1-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 61660253   183 LRCFARDYYPADLEIRWWKDdggGGALPQTSKQhHDPLPSGNGLYQKHidVYV-----DGGLEHVYSCRVK 248
Cdd:pfam07654  17 LTCLVTGFYPPDITVTWLKN---GQEVTEGVKT-TPPSPNSDWTYQLS--SYLtvtpsDWESGDEYTCRVE 81

Class I major histocompatibility complex (MHC) homolog m144; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) domain of major histocompatibility complex (MHC) homolog m144 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 61660253 163 AVSPQLEVERRSSGREGGMRLRCFARDYYPADLEIRWWKDDGGGGALPQTSKQHHDPLPSGNGLYQKHIDVYVDGGLEHV 242
Cdd:cd21028   1 AVSPQLEVERRSSGREGGMRLRCFARDYYPADLEIRWWKDDGGGGALPQTSKQHHDPLPSGNGLYQKHIDVYVDGGLEHV 80

                        90       100
                ....*....|....*....|.
gi 61660253 243 YSCRVKGIATGLELQIVRWKG 263
Cdd:cd21028  81 YSCRVKGIATGLELQIVRWKG 101

Immunoglobulin domain of Cluster of Differentiation (CD) 1; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin domain of Cluster of Differentiation (CD) 1. CD1 family of transmembrane glycoproteins, are structurally related to the major histocompatibility complex (MHC) proteins and form heterodimers with beta-2-microglobulin. They mediate the presentation of primarily lipid and glycolipid antigens of self or microbial origin to T cells. The human genome contains five CD1 family genes (CD1a, CD1b, CD1c, CD1d, and CD1e) organized in a cluster on chromosome 1. The CD1 family members are thought to differ in their cellular localization and specificity for particular lipid ligands. CD1a localizes to the plasma membrane and to recycling vesicles of the early endocytic system. Alternative splicing results in multiple transcript variants. 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. C1-set Ig domains have one beta sheet that is formed by strands A, B, E, and D and the other strands by G, F, C, and C'.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 61660253 164 VSPQLEVERRSSGREGGMRLRCFARDYYPADLEIRWWKDdgggGALPQTSKQHHDPLPSGNGLYQKHIDVYVDGGLEHVY 243
Cdd:cd21029   1 VKPRVRLSSRPSPGDGHLQLSCHVTGFYPRPIEVTWLRD----GQEQMDGTQSGGILPNHDGTYQLRKTLDIAPGEGAGY 76

                ....*
gi 61660253 244 SCRVK 248
Cdd:cd21029  77 SCRVD 81

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of T10, T22, and similar proteins; 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 the murine H-2T-encoded T10, T22, and similar proteins. T10 and T22 are highly related nonclassical major histocompatibility complex (MHC) class Ib proteins that bind to certain gammadelta T cell receptors (TCRs) in the absence of other components. Classical MHC class I (class Ia) molecules participate in immune responses by presenting peptide antigens to cytolytic alpha beta T cells. Many nonclassical MHC class I (class Ib) molecules have distinct antigen-binding capabilities, suggesting that they have evolved for specific tasks that are distinct from those of MHC class Ia. 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 61660253 166 PQLEVERRSSgREGGMRLRCFARDYYPADLEIRWWKDdggGGALPQtSKQHHDPLPSGNGLYQKHIDVYVDGGLEHVYSC 245
Cdd:cd21016   6 PKAHVTRHPR-PEGDVTLRCWALGFYPADITLTWQKD---GEELTQ-DMEFVETRPAGDGTFQKWAAVVVPLGKEQSYTC 80

                        90       100
                ....*....|....*....|
gi 61660253 246 RV--KGIATGLelqIVRWKG 263
Cdd:cd21016  81 HVyhEGLPEPL---TLRWEP 97

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
                ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 61660253 178 EGGMRLRCFARDYYPADLEIRWWKDdggGGALPQTSKQHHDPLPSGNGLYQKHIDVYVDGGLEHVYSC 245
Cdd:cd21017  16 EGNITVTCRASGFYPWNITLSWRQD---GVSLSHDTQQWGDVLPDGNGTYQTWVATRICQGEEQRFTC 80

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
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 61660253 178 EGGMRLRCFARDYYPADLEIRWWKDdggGGALPQtSKQHHDPLPSGNGLYQKHIDVYVDGGLEHVYSCRVK 248
Cdd:cd21015  16 EGDVTLRCWALGFYPADITLTWQLN---GEDLTQ-DMELVETRPAGDGTFQKWASVVVPLGKEQNYTCRVE 82

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) H2Db and H2Ld; 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) H2Db and H2Ld. H-2Ld complexed with peptide QL9 (or p2Ca) and complexed with influenza virus peptide NP366-374 (ASNEN-METM), respectively are high-affinity alloantigens for the 2C T cell receptor (TCR). The a1-a2 super domains of H-2Ld, H-2Db, and H-2Kb closely superimpose. 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 61660253 165 SPQLEVERRSSGReGGMRLRCFARDYYPADLEIRWWKDdggGGALPQtSKQHHDPLPSGNGLYQKHIDVYVDGGLEHVYS 244
Cdd:cd21018   5 SPKAHVTHHPRSK-GEVTLRCWALGFYPADITLTWQLN---GEELTQ-DMELVETRPAGDGTFQKWASVVVPLGKEQNYT 79

                        90
                ....*....|....*....
gi 61660253 245 CRV--KGIATGLELqivRW 261
Cdd:cd21018  80 CRVyhEGLPEPLTL---RW 95

Immunoglobulin C1-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 61660253   183 LRCFARDYYPADLEIRWWKDdggGGALPQTSKQhHDPLPSGNGLYQKHidVYV-----DGGLEHVYSCRVK 248
Cdd:pfam07654  17 LTCLVTGFYPPDITVTWLKN---GQEVTEGVKT-TPPSPNSDWTYQLS--SYLtvtpsDWESGDEYTCRVE 81

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 61660253 183 LRCFARDYYPADLEIRWWKDdgGGGALPQTskQHHDPLPSGNGLYQKHIDVYVDGGLEHVYSCRVKgiATGL-ELQIVRW 261
Cdd:cd21024  22 LRCWALGFYPAEITLTWQQD--GEGHTQDT--ELVETRPAGDGTFQKWAAVVVPSGEEQRYTCHVQ--HEGLpEPVTLRW 95

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 61660253 179 GGMRLRCFARDYYPADLEIRWWKDdggGGALPQtSKQHHDPLPSGNGLYQKHIDVYVDGGLEHVYSCRV--KGIATGLEL 256
Cdd:cd21014  17 GAVTLRCWALGFYPADITLTWQLN---GEELTQ-DMELVETRPAGDGTFQKWASVVVPLGKEQNYTCHVnhEGLPEPLTL 92

                ....*
gi 61660253 257 qivRW 261
Cdd:cd21014  93 ---RW 94

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of H-2Kb; 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 H-2Kb. H-2Kb is an alloantigen for the 2C T cell receptor (TCR). H-2Kb forms a complex with beta-2-microglobulin, and a peptide, including VSV-8 (RGYVYNGL), SEV-9 (FAPGNYPAL), and OVA-8 (SIINFEKL). Comparison of the OVA-8, VSV-8, and SEV-9 complexes with H-2Kb indicates that four side chains (Lys-66, Glu-152, Arg-155, and Trp-167) adopt peptide-specific conformations. H-2Kb paralogs include H-2Db, H-2Kbml and H-2KbI1s. 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 61660253 165 SPQLEVERRSSgREGGMRLRCFARDYYPADLEIRWWKDdggGGALPQtSKQHHDPLPSGNGLYQKHIDVYVDGGLEHVYS 244
Cdd:cd21019   4 SPKAHVTHHSR-PEDKVTLRCWALGFYPADITLTWQLN---GEELIQ-DMELVETRPAGDGTFQKWASVVVPLGKEQYYT 78

                        90
                ....*....|....*....
gi 61660253 245 CRV--KGIATGLELqivRW 261
Cdd:cd21019  79 CHVyhQGLPEPLTL---RW 94

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 61660253 178 EGGMRLRCFARDYYPADLEIRWWKDdggGGALPQtSKQHHDPLPSGNGLYQKHIDVYVDGGLEHVYSCRV--KGIATGLE 255
Cdd:cd21020  17 EGDVTLRCWALGFYPADITLTWQLN---GEELTQ-EMELVETRPAGDGTFQKWASVVVPLGKEQKYTCHVehEGLPEPLT 92

                ....*.
gi 61660253 256 LqivRW 261
Cdd:cd21020  93 L---RW 95

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 61660253 178 EGGMRLRCFARDYYPADLEIRWWKDdggGGALPQtSKQHHDPLPSGNGLYQKHIDVYVDGGLEHVYSCRV--KGIATGLE 255
Cdd:cd21820  17 EDEVTLRCWALGFYPADITLTWQLN---GEELTQ-DMELVETRPAGDGTFQKWAAVVVPLGKEQYYTCHVyhEGLPEPLT 92

                ....*..
gi 61660253 256 LqivRWK 262
Cdd:cd21820  93 L---RWE 96

Class I major histocompatibility complex (MHC) beta-2-microglobulin; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin-like domain in beta-2-microglobulin (beta2m). Beta2m is the non-covalently bound light chain of the human class I major histocompatibility complex (MHC-I). Beta2m is structured as a beta-sandwich domain composed of two facing beta-sheets (four stranded and three stranded), that is typical of the C-type immunoglobulin superfamily. This structure is stabilized by an intramolecular disulfide bridge connecting two Cys residues in the facing beta-sheets. In vivo, MHC-I continuously exposes beta2m on the cell surface, where it may be released to plasmatic fluids, transported to the kidneys, degraded, and finally excreted.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 61660253 164 VSPQLEVERRSSGREGGMR-LRCFARDYYPADLEIRWWKDdggGGALPQTskQHHDPLPSGNGLYQ--KHIDVYVDGGLE 240
Cdd:cd05770   1 STPKVQVYSRFPAENGKPNvLNCYVSGFHPPDIEIRLLKN---GVKIEDV--EQSDLSFSKDWTFYllKYTEFTPTKGDE 75

                        90       100
                ....*....|....*....|.
gi 61660253 241 hvYSCRVKGiATGLELQIVRW 261
Cdd:cd05770  76 --YACRVRH-NTLSEPKIYKW 93

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DM; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DM. Human HLA-DM plays a critical role in antigen presentation to CD4 T cells by catalyzing the exchange of peptides bound to MHC class II molecules. Type 1 diabetes is correlated with DM activation and it is also implicated in viral infections such as herpes simplex virus, celiac disease, multiple sclerosis, other autoimmune diseases, and leukemia. 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 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
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 61660253 182 RLRCFARDYYPADLEIRWWKDdggGGALPQTSKQHHDPLPSGNGLYQKHIDVYVDGGLEHVYSCRVKGIAT 252
Cdd:cd21002  21 MLACHVWGFYPADVTITWLKN---GDPVAPHSSAPKTAQPNGDWTYQTQVTLAVTPSPGDTYTCSVQHASL 88