Class I Histocompatibility antigen, domains alpha 1 and 2;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30385096     1 SHSLRYFYTSLSWSAISEPWYIAVGYLDDTQFVRFHSIGETATYKLRVPWVEQEGPEYWARETEIVTSNAQFFRGNLQTM 80
Cdd:pfam00129   2 SHSLRYFYTAVSRPGLGEPRFIAVGYVDDTQFVRFDSDAANPRMEPRAPWIEQEGPEYWERETQIAKGNEQIFRENLRTL 81

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30385096    81 FDYYNLSQNGSHTIQVMYGCEVESDGSFLRAYEKHGYDGRDYISLNEDLKTWTAADMEAEITRSKWERDGYAELRRTYLE 160
Cdd:pfam00129  82 LGYYNQSEGGSHTLQWMYGCDVGPDGRLLRGYEQFAYDGKDYIALNEDLRSWTAADPAAQITKRKWEAAGEAERQRAYLE 161

                         170
                  ....*....|....*...
gi 30385096   161 GPCKDSLLRYLEDRKKTQ 178
Cdd:pfam00129 162 GECVEWLRRYLENGKETL 179

Class I Histocompatibility antigen, domains alpha 1 and 2;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30385096     1 SHSLRYFYTSLSWSAISEPWYIAVGYLDDTQFVRFHSIGETATYKLRVPWVEQEGPEYWARETEIVTSNAQFFRGNLQTM 80
Cdd:pfam00129   2 SHSLRYFYTAVSRPGLGEPRFIAVGYVDDTQFVRFDSDAANPRMEPRAPWIEQEGPEYWERETQIAKGNEQIFRENLRTL 81

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30385096    81 FDYYNLSQNGSHTIQVMYGCEVESDGSFLRAYEKHGYDGRDYISLNEDLKTWTAADMEAEITRSKWERDGYAELRRTYLE 160
Cdd:pfam00129  82 LGYYNQSEGGSHTLQWMYGCDVGPDGRLLRGYEQFAYDGKDYIALNEDLRSWTAADPAAQITKRKWEAAGEAERQRAYLE 161

                         170
                  ....*....|....*...
gi 30385096   161 GPCKDSLLRYLEDRKKTQ 178
Cdd:pfam00129 162 GECVEWLRRYLENGKETL 179

Immunoglobulin C-Type;

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 30385096    198 VTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPS---GEEQKYTCHVYHEGLPEP 268
Cdd:smart00407   2 ATLVCLVSGFYPPDITVTWLRNGQEVTEGVSTTDPLKNSDGTYFLSSYLTVPAstwESGDVYTCQVTHEGLKEP 75

Class I Histocompatibility antigen, domains alpha 1 and 2;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30385096     1 SHSLRYFYTSLSWSAISEPWYIAVGYLDDTQFVRFHSIGETATYKLRVPWVEQEGPEYWARETEIVTSNAQFFRGNLQTM 80
Cdd:pfam00129   2 SHSLRYFYTAVSRPGLGEPRFIAVGYVDDTQFVRFDSDAANPRMEPRAPWIEQEGPEYWERETQIAKGNEQIFRENLRTL 81

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30385096    81 FDYYNLSQNGSHTIQVMYGCEVESDGSFLRAYEKHGYDGRDYISLNEDLKTWTAADMEAEITRSKWERDGYAELRRTYLE 160
Cdd:pfam00129  82 LGYYNQSEGGSHTLQWMYGCDVGPDGRLLRGYEQFAYDGKDYIALNEDLRSWTAADPAAQITKRKWEAAGEAERQRAYLE 161

                         170
                  ....*....|....*...
gi 30385096   161 GPCKDSLLRYLEDRKKTQ 178
Cdd:pfam00129 162 GECVEWLRRYLENGKETL 179

Class I major histocompatibility complex (MHC) alpha chain, alpha3 immunoglobulin domain; 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) 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 30385096 182 DPPKTHVTHHPRPEGDVTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHVY 261
Cdd:cd07698   1 DPPKVHVTHHPRSDGESTLRCWALGFYPAEITLTWQRDGEDQTQDMELVETRPNGDGTFQKWAAVVVPSGEEQRYTCHVQ 80

                        90
                ....*....|..
gi 30385096 262 HEGLPEPLTLRW 273
Cdd:cd07698  81 HEGLPEPLTLRW 92

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 30385096 181 TDPPKTHVTHHPRPEGDVTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHV 260
Cdd:cd21820   3 SDPPKAHVTHHPRSEDEVTLRCWALGFYPADITLTWQLNGEELTQDMELVETRPAGDGTFQKWAAVVVPLGKEQYYTCHV 82

                        90
                ....*....|...
gi 30385096 261 YHEGLPEPLTLRW 273
Cdd:cd21820  83 YHEGLPEPLTLRW 95

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 30385096 181 TDPPKTHVTHHPRPEGDVTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHV 260
Cdd:cd21019   2 TDSPKAHVTHHSRPEDKVTLRCWALGFYPADITLTWQLNGEELIQDMELVETRPAGDGTFQKWASVVVPLGKEQYYTCHV 81

                        90
                ....*....|...
gi 30385096 261 YHEGLPEPLTLRW 273
Cdd:cd21019  82 YHQGLPEPLTLRW 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 30385096 181 TDPPKTHVTHHPRPEGDVTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHV 260
Cdd:cd21020   3 TDPPKAHVTHHRRPEGDVTLRCWALGFYPADITLTWQLNGEELTQEMELVETRPAGDGTFQKWASVVVPLGKEQKYTCHV 82

                        90
                ....*....|...
gi 30385096 261 YHEGLPEPLTLRW 273
Cdd:cd21020  83 EHEGLPEPLTLRW 95

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 30385096 181 TDPPKTHVTHHPRPEGDVTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHV 260
Cdd:cd21015   2 SDPPEAHVTLHPRPEGDVTLRCWALGFYPADITLTWQLNGEDLTQDMELVETRPAGDGTFQKWASVVVPLGKEQNYTCRV 81

                        90
                ....*....|...
gi 30385096 261 YHEGLPEPLTLRW 273
Cdd:cd21015  82 EHEGLPKPLSQRW 94

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) F; 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 alpha chain F (HLA-F). HLA-F, encoded by the HLA-F gene in humans, belongs to the non-classical HLA class I heavy chain paralogs. This class I molecule mainly exists as a heterodimer associated with the invariant light chain beta-2-microglobulin. HLA-F molecules can interact with both activating and inhibitory receptors on immune cells, such as NK cells, and can present a diverse panel of peptides. 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 30385096 182 DPPKTHVTHHPRPEGDVTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHVY 261
Cdd:cd21023   4 DPPKAHVAHHPISDHEATLRCWALGFYPAEITLTWQRDGEEQTQDTELVETRPAGDGTFQKWAAVVVPPGEEQRYTCHVQ 83

                        90
                ....*....|..
gi 30385096 262 HEGLPEPLTLRW 273
Cdd:cd21023  84 HEGLPQPLILRW 95

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 30385096 184 PKTHVTHHPRPEGDVTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHVYHE 263
Cdd:cd21025   6 PKTHVTHHPVSDHEATLRCWALGFYPAEITLTWQWDGEDQTQDTELVETRPAGDGTFQKWAAVVVPSGEEQRYTCHVQHE 85

                        90
                ....*....|
gi 30385096 264 GLPEPLTLRW 273
Cdd:cd21025  86 GLPEPLTLRW 95

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 30385096 181 TDPPKTHVTHHPRPEGDVTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHV 260
Cdd:cd21027   3 TDAPKTHMTHHAVSDHEATLRCWALSFYPAEITLTWQRDGEDQTQDTELVETRPAGDGTFQKWAAVVVPSGQEQRYTCHV 82

                        90
                ....*....|...
gi 30385096 261 YHEGLPEPLTLRW 273
Cdd:cd21027  83 QHEGLPKPLTLRW 95

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 30385096 182 DPPKTHVTHHPRPEGDVTLRCWALGFYPADITLTWQLNGEelIQDTEL-VETRPAGDGTFQKWAAVVVPSGEEQKYTCHV 260
Cdd:cd21010   3 DPPSVSVTSHVAPGKNRTLKCLAYDFYPRGISLHWTRAGK--VQESESgGDVLPSGNGTYQSWVVVEVPPQDRAPYSCHV 80

                        90
                ....*....|...
gi 30385096 261 YHEGLPEPLTLRW 273
Cdd:cd21010  81 EHSSLAQPLTVPW 93

Immunoglobulin Constant-1 (C1)-set domain; The members here are composed of C1-set domains, classical Ig-like domains resembling the antibody constant domain. Members of the IgC1 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, while the IgC domain is involved in oligomerization and molecular interactions. 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 strands by G, F, C, and C'.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30385096 187 HVTHHP-----RPEGDVTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQK---YTC 258
Cdd:cd00098   1 TVTLLPpspeeKGGGKVTLVCLVSGFYPKDITVTWLKNGVPLTSGVSTSSPVEPNDGTYSVTSSLTVPPSDWDEgatYTC 80

                        90
                ....*....|....*
gi 30385096 259 HVYHEGLPEPLTLRW 273
Cdd:cd00098  81 VVTHESLKSPLSKTW 95

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 30385096 181 TDPPKTHVTHHPRPEGDVTLRCWALGFYPADITLTWQLNGEELIQDT-ELVETRPAGDGTFQKWAAVVVPSGEEQKYTCH 259
Cdd:cd21017   2 TVPPMVNVTRSEASEGNITVTCRASGFYPWNITLSWRQDGVSLSHDTqQWGDVLPDGNGTYQTWVATRICQGEEQRFTCY 81

                ....*
gi 30385096 260 VYHEG 264
Cdd:cd21017  82 MEHSG 86

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain; 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) class II beta 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 has 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 30385096 183 PPKTHVTHHPrpegdVTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHVYH 262
Cdd:cd05766  10 PTKTGPLEHP-----NLLVCSVTGFYPAEIEVKWFRNGQEETAGVVSTELIPNGDWTFQILVMLETTPRRGDVYTCQVEH 84

                        90
                ....*....|.
gi 30385096 263 EGLPEPLTLRW 273
Cdd:cd05766  85 SSLQSPLTVDW 95

Tapasin-R immunoglobulin-like domain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin-like domain on Tapasin-R. Tapasin is a V-C1 (variable-constant) immunoglobulin superfamily molecule present in the endoplasmic reticulum (ER), where it links MHC class I molecules to the transporter associated with antigen processing (TAP). Tapasin-R is a tapasin-related protein that contains similar structural motifs to Tapasin, with some marked differences, especially in the V domain, transmembrane and cytoplasmic regions. The majority of Tapasin-R is located within the ER; however, there may be some expression of Tapasin-R at the cell surface. Tapasin-R lacks an obvious ER retention signal.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30385096 194 PEGDVTLRCWALGFYPADITLTWQLNG------EELIQDTELVETRPAGDGTFQKWAAVVVPSGEE---QKYTCHVYHEG 264
Cdd:cd05771  13 PDLPQTLSCHIAGYYPLDVDVEWLREEpggsesQVSRDGVSLSSHRQSVDGTYSISSYLTLEPGTEnrgATYTCRVTHVS 92

                ....*..
gi 30385096 265 LPEPLTL 271
Cdd:cd05771  93 LEEPLSV 99

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 30385096 183 PPKTHV-THHPRPEGDV-TLRCWALGFYPADITLTWQLNGEElIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHV 260
Cdd:cd05770   2 TPKVQVySRFPAENGKPnVLNCYVSGFHPPDIEIRLLKNGVK-IEDVEQSDLSFSKDWTFYLLKYTEFTPTKGDEYACRV 80

                        90
                ....*....|...
gi 30385096 261 YHEGLPEPLTLRW 273
Cdd:cd05770  81 RHNTLSEPKIYKW 93

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.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 30385096 199 TLRCWALGFYPADITLTWQLNGEELiqdTELV-ETR--PAGDGTFQKWAAV-VVPSgEEQKYTCHVYHEGLPEPLTLRW 273
Cdd:cd05767  20 TLICFVDNFFPPVINVTWLRNGQPV---TDGVsETVflPREDHSFRKFSYLpFTPS-EGDIYDCRVEHWGLEEPLLKHW 94

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DR; 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) DR. HLA-DR is an MHC class II cell surface receptor encoded by the human leukocyte antigen complex on chromosome 6 region 6p21.31. HLA-DR is also involved in several autoimmune conditions, disease susceptibility, and disease resistance including seronegative-rheumatoid arthritis, penicillamine-induced myasthenia, schizophrenia, Goodpasture syndrome, systemic lupus erythematosus, Alzheimers, tuberculoid leprosy, and Hashimoto's thyroiditis. HLA-DR molecules are upregulated in response to signaling. HLA-DR is an alphabeta heterodimer cell surface receptor, each subunit of which contains two extracellular domains, a membrane-spanning domain, and a cytoplasmic tail. Both alpha and beta chains are anchored in the membrane. The DR beta chain is encoded by 4 loci, however no more than 3 functional loci are present in a single individual, and no more than two on a single chromosome. Sometimes an individual may only possess 2 copies of the same locus, DRB1*. The HLA-DRB1 locus is ubiquitous and encodes a very large number of functionally variable gene products (HLA-DR1 to HLA-DR17). The HLA-DRB3 locus encodes the HLA-DR52 specificity, is moderately variable and is variably associated with certain HLA-DRB1 types. The HLA-DRB4 locus encodes the HLA-DR53 specificity, has some variation, and is associated with certain HLA-DRB1 types. The HLA-DRB5 locus encodes the HLA-DR51 specificity, which is typically invariable, and is linked to the HLA-DR2 types. Three genetically distinct isotypes of class II MHC molecules are found in humans (HLA-DR, HLA-DQ, and HLA-DP), and two in mice (I-E and I-A). 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        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30385096 183 PPKTH-VTHHPrpegdvTLRCWALGFYPADITLTWQLNGEEL---IQDTELVETrpaGDGTFQKWAAV-VVP-SGEeqKY 256
Cdd:cd21000  10 PAKTQpLQHHN------LLVCSVNGFYPGSIEVRWFRNGQEEkagVVSTGLIQN---GDWTFQTLVMLeTVPrSGE--VY 78

                        90
                ....*....|....*..
gi 30385096 257 TCHVYHEGLPEPLTLRW 273
Cdd:cd21000  79 TCQVEHPSVTSPLTVEW 95

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) I-E; 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) I-E. Three genetically distinct isotypes of class II MHC molecules are found in humans (HLA-DR, HLA-DQ, and HLA-DP), and two in mice (I-E and I-A). I-A and I-E molecules have the same basic features insofar as peptide loading and presentation, although each interacts with distinctly different sets of peptides. They also differ in that there is a relatively high incidence of deletion of the I-E gene in both inbred strains of mice as well as wild mice and the lack of the reverse situation i.e. the deletion of I-A genes. A detailed structural understanding of the similarities and differences between I-A and the paralogous I-E could help illuminate the respective roles these molecules play in peptide presentation and T cell activation. Mouse I-Ag7 has a genetic susceptibility to autoimmune diabetes due to its small, uncharged amino acid residue at position 57 of their beta chain which results in the absence of a salt bridge between beta 57 and Arg alpha 76, which is adjacent to the P9 pocket of the peptide-binding groove. 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        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30385096 183 PPKTHVTHHPRpegdvTLRCWALGFYPADITLTWQLNGEEliQDTELVETRPA--GDGTFQKWAAVVVPSGEEQKYTCHV 260
Cdd:cd20998  13 PTKTQPLEHHN-----LLVCSVSDFYPGNIEVRWFRNGKE--EKTGIVSTGLVrnGDWTFQTLVMLETVPQSGEVYTCQV 85

                        90
                ....*....|...
gi 30385096 261 YHEGLPEPLTLRW 273
Cdd:cd20998  86 EHPSLTDPVTVEW 98

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 30385096 195 EGDVTLRCWALGFYPADITLTWQLN---GEELIQDT-ELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHVyhEGLPEPLT 270
Cdd:cd21028  16 EGGMRLRCFARDYYPADLEIRWWKDdggGGALPQTSkQHHDPLPSGNGLYQKHIDVYVDGGLEHVYSCRV--KGIATGLE 93

                ....*.
gi 30385096 271 L---RW 273
Cdd:cd21028  94 LqivRW 99

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DQ and I-A; 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 human histocompatibility antigen (HLA) DQ and mouse I-A. Three genetically distinct isotypes of class II MHC molecules are found in humans (HLA-DR, HLA-DQ, and HLA-DP), and two in mice (I-E and I-A). I-A and I-E have the same basic features insofar as peptide loading and presentation, they differ in that each interacts with distinctly different sets of peptides, and in the incidence of deletion of their genes. A structural understanding of the similarities and differences between I-A and I-E may help with understanding their roles in peptide presentation and T cell activation. Mouse I-Ag7 has a genetic susceptibility to autoimmune diabetes due to its small, uncharged amino acid residue at position 57 of their beta chain which results in the absence of a salt bridge between beta 57 and Arg alpha 76, which is adjacent to the P9 pocket of the peptide-binding groove. Human HLA-DR, -DQ, and -DP are about 70% similar to each other. HLA-DQ (DQ) is a cell surface receptor protein found on antigen presenting cells. It is an alphabeta heterodimer of type MHC class II. The alpha and beta chains are encoded by two loci, HLA-DQA1 and HLA-DQB1, that are adjacent to each other on chromosome band 6p21.3. A person often produces two alpha-chain and two beta chain variants and thus 4 isoforms of DQ. HLA-DQ is involved in the autoimmune diseases celiac disease and diabetes mellitus type. DQ is one of several antigens involved in rejection of organ transplants. DQ2 is encoded by the HLA-DQB1*02 allele group. DQ6 is encoded by the HLA-DQB1*06 allele group. DQ2 beta-chains combine with alpha-chains, encoded by genetically linked HLA-DQA1 alleles, to form the cis-haplotype isoforms. These isoforms, nicknamed DQ2.2 and DQ2.5, are also encoded by the DQA1*0201 and DQA1*0501 genes, respectively. DQ6 beta-chains combine with alpha-chains, encoded by genetically linked HLA-DQA1 alleles, to form the cis-haplotype isoforms. For DQ6, however, cis-isoform pairing only occurs with DQ1 alpha-chains. There are many haplotypes of DQ6. Susceptibility to Leptospirosis infection was found associated with undifferentiated DQ6. DQ8 is determined by the antibody recognition of beta8 and this generally detects the gene product of DQB1*0302. DQ8 is commonly linked to autoimmune disease in the human population. DQ8 is the second most predominant isoform linked to celiac disease and the DQ most linked to Type 1 diabetes. DQ8 increases the risk for rheumatoid arthritis and is linked to the primary risk locus for RA, HLA-DR4. DR4 also plays an important role in Type 1 diabetes. DQ8 is a split antigen of the DQ3 broad antigen. MHC class II molecules play a key role in the initiation of the antigen-specific immune response. They are expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice, and induced in nonprofessional APCs, such as keratinocyctes; they are expressed on the surface of activated human T cells and on T cells from other species. 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, and 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 30385096 183 PPKTHV-THHPrpegdvTLRCWALGFYPADITLTWQLNGEEliqDTELVETRPA---GDGTFQKWAAVVVPSGEEQKYTC 258
Cdd:cd21001  10 PSRTEAlNHHN------LLVCSVTDFYPGQIKVRWFRNDQE---ETAGVVSTPLirnGDWTFQILVMLEMTPQRGDVYTC 80

                        90
                ....*....|....*
gi 30385096 259 HVYHEGLPEPLTLRW 273
Cdd:cd21001  81 HVEHPSLQSPITVEW 95

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.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 30385096 198 VTLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDG--TFQKWAAVVVPSGE---EQKYTCHVYHEGL 265
Cdd:cd16093  20 ATFVCLATGFSPKTISFKWLRNGKEVTSSTGAVVEEPKEDGktLYSATSFLTITESEwksQTEFTCEFKHKGE 92

Class II major histocompatibility complex (MHC) alpha chain immunoglobulin domain of histocompatibility antigen (HLA) DR; 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) class II alpha chain of histocompatibility antigen (HLA) DR. MHC class II molecules are encoded by three different loci, HLA-DR, -DQ, and -DP, which are about 70% similar to each other. HLA-DR is a cell surface receptor protein found on antigen presenting cells. It is an alphabeta heterodimer of type MHC class II. The alpha and beta chains are encoded by two loci, HLA-DRA1 and HLA-DRB1, that are adjacent to each other on chromosome band 6p21.31. Susceptibility to multiple sclerosis and rheumatoid arthritis are associated with the human histocompatibility leukocyte antigen HLA-DR2 and HLA-DR4, respectively. 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 30385096 200 LRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHVYHEGLPEPLTLRW 273
Cdd:cd21007  21 LICFIDKFTPPVVNVTWLRNGKPVTTGVSETVFLPREDHLFRKFHYLPFLPSTEDVYDCRVEHWGLDEPLLKHW 94

Class II major histocompatibility complex (MHC) alpha chain immunoglobulin domain of histocompatibility antigen (HLA) I-E; 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) class II alpha chain of histocompatibility antigen (HLA) I-E. 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 30385096 200 LRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHVYHEGLPEPLTLRW 273
Cdd:cd21005  21 LICFIDKFSPPVVNVTWLRNGRPVTEGVSETVFLPRDDHLFRKFHYLTFLPSTDDFYDCEVDHWGLEEPLRKHW 94

CH1 domain (first constant Ig domain of the heavy chain) in immunoglobulin heavy epsilon and gamma chain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the first immunoglobulin constant-1 set domain of epsilon and gamma chains. It belongs to a family composed of the first immunoglobulin constant-1 set domain of alpha, delta, epsilon, gamma, and mu heavy chains. This domain is found on the Fab antigen-binding 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. This group belongs to the C1-set of IgSF domains, which are classical Ig-like domains resembling the antibody constant domain. C1-set domains are found almost exclusively in molecules involved in the immune system, such as in immunoglobulin light and heavy chains, in the major histocompatibility complex (MHC) class I and II complex molecules, and in various T-cell receptors.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 30385096 194 PEGDVTLRCWALGFYPADITLTWqlNGEELiqdTELVETRPA---GDGTFQKWAAVVVPSGE--EQKYTCHVYH 262
Cdd:cd21817  15 NGSSVTLGCLVTGYFPEPVTVTW--NSGSL---TSGVKTFPAvlqSSGLYTTSSQVTVPSSSwgSQTFTCNVEH 83

CH1 domain (first constant Ig domain of the heavy chain) in immunoglobulin heavy alpha, delta, epsilon, gamma, and mu chains; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the first immunoglobulin constant-1 set domain of alpha, delta, epsilon, gamma, and mu heavy chains. This domain is found on the Fab antigen-binding 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. This group belongs to the C1-set of IgSF domains, which are classical Ig-like domains resembling the antibody constant domain. C1-set domains are found almost exclusively in molecules involved in the immune system, such as in immunoglobulin light and heavy chains, in the major histocompatibility complex (MHC) class I and II complex molecules, and in various T-cell receptors.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 30385096 194 PEGDVTLRCWALGFYPADITLTWQLNGEELIQDTelVETRPA---GDGTFQKWAAVVVPS---GEEQKYTCHVYH 262
Cdd:cd04985  15 SNGPVALGCLISDYFPESITVSWQKNTNSITSGF--TRTFPVvlrSGGDYSCSSQLTVPLqewNSGEVYKCQVQH 87

CD80-like C2-set immunoglobulin domain; These domains belong to the immunoglobulin superfamily.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 30385096   198 VTLRCWALGFYPAdITLTWQLNGEELIQDTELVETRPAGdGTF---QKWAAVVVPSGEEQKYTCHVYHEGLPEP 268
Cdd:pfam08205  17 VVATCSSAGGKPA-PRITWYLDGKPLEAAETSSEQDPES-GLVtvtSELKLVPSRSDHGQSLTCQVSYGALRGS 88

HLA class II histocompatibility antigen DO alpha; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the nonclassical MHC class II (MHCII) protein, HLA-DO, which binds HLA-DM and influences the repertoire of peptides presented by MHCII proteins. In complex with HLA-DM, HLA-DO adopts a classical MHCII structure, with alterations near the a subunit's 310 helix. HLA-DO binds to HLA-DM at the same sites implicated in MHCII interaction, and kinetic analysis showed that HLA-DO acts as a competitive inhibitor by acting as a substrate mimic. Though more remains to be elucidated about the function of HLA-DO, its unique distribution in the mammalian body namely, the exclusive expression of HLA-DO in B cells, thymic medullary epithelial cells, and dendritic cells indicate that it may be of physiological importance and has inspired further research. 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 30385096 183 PPKthVTHHPRPEGDV----TLRCWALGFYPADITLTWQLNGEELIQDTELVETRPAGDGTFQKWAAVV-VPSGEEQkYT 257
Cdd:cd21004   2 PPR--VTVLPKSRVELgqpnILICIVDNIFPPVINITWLRNGQTVTEGVAQTSFYSQPDHLFRKFHYLPfVPSAEDV-YD 78

                        90
                ....*....|....*.
gi 30385096 258 CHVYHEGLPEPLTLRW 273
Cdd:cd21004  79 CKVEHWGLDRPLLRHW 94