Second immunoglobulin (Ig)-like domain of Fcgamma-receptors (FcgammaRs), and similar domains; The members here are composed of the second immunoglobulin (Ig)-like domain of Fcgamma-receptors (FcgammaRs). Interactions between IgG and FcgammaR are important to the initiation of cellular and humoral response. IgG binding to FcgammaR leads to a cascade of signals and ultimately to functions such as antibody-dependent-cellular-cytotoxicity (ADCC), endocytosis, phagocytosis, release of inflammatory mediators, etc. FcgammaR has two Ig-like domains. This group also contains FcepsilonRI which binds IgE with high affinity.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783  128 WLLLQTPQLVFLEGETITLRCHSWRNKLLNRISFFHNEKSVRYHHYSSNFSIPKANHSHSGDYYCKGSLGRTLHQSKPVT 207
Cdd:cd05753   1 WLLLQAPSAVVFEGEPLTLRCHGWKDKKVHKVTYYKDGKALKFSYENSNFSIPQATLSDSGSYHCSGTVRIKRRSSESVN 80

                ...
gi 6857783  208 ITV 210
Cdd:cd05753  81 ITV 83

Second immunoglobulin (Ig)-like domain of Fcgamma-receptors (FcgammaRs), and similar domains; The members here are composed of the second immunoglobulin (Ig)-like domain of Fcgamma-receptors (FcgammaRs). Interactions between IgG and FcgammaR are important to the initiation of cellular and humoral response. IgG binding to FcgammaR leads to a cascade of signals and ultimately to functions such as antibody-dependent-cellular-cytotoxicity (ADCC), endocytosis, phagocytosis, release of inflammatory mediators, etc. FcgammaR has two Ig-like domains. This group also contains FcepsilonRI which binds IgE with high affinity.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783  128 WLLLQTPQLVFLEGETITLRCHSWRNKLLNRISFFHNEKSVRYHHYSSNFSIPKANHSHSGDYYCKGSLGRTLHQSKPVT 207
Cdd:cd05753   1 WLLLQAPSAVVFEGEPLTLRCHGWKDKKVHKVTYYKDGKALKFSYENSNFSIPQATLSDSGSYHCSGTVRIKRRSSESVN 80

                ...
gi 6857783  208 ITV 210
Cdd:cd05753  81 ITV 83

Immunoglobulin domain; This domain contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783    128 WLLLQTPQLVFLEGETITLRCHSWRNKLLNrISFFHNEKSVRYHHyssNFSIPKANHSHSGDYYCKGSLGRTLHQSKPVT 207
Cdd:pfam13895   1 KPVLTPSPTVVTEGEPVTLTCSAPGNPPPS-YTWYKDGSAISSSP---NFFTLSVSAEDSGTYTCVARNGRGGKVSNPVE 76

                  ...
gi 6857783    208 ITV 210
Cdd:pfam13895  77 LTV 79

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783     134 PQLVFLEGETITLRCH---------SWRNKLLNRIsFFHNEKSVRYHHYSSNFSIPKANHSHSGDYYCKGSLGRTLHQSk 204
Cdd:smart00410   2 PSVTVKEGESVTLSCEasgspppevTWYKQGGKLL-AESGRFSVSRSGSTSTLTISNVTPEDSGTYTCAATNSSGSASS- 79

                   ....*.
gi 6857783     205 PVTITV 210
Cdd:smart00410  80 GTTLTV 85

Second immunoglobulin (Ig)-like domain of Fcgamma-receptors (FcgammaRs), and similar domains; The members here are composed of the second immunoglobulin (Ig)-like domain of Fcgamma-receptors (FcgammaRs). Interactions between IgG and FcgammaR are important to the initiation of cellular and humoral response. IgG binding to FcgammaR leads to a cascade of signals and ultimately to functions such as antibody-dependent-cellular-cytotoxicity (ADCC), endocytosis, phagocytosis, release of inflammatory mediators, etc. FcgammaR has two Ig-like domains. This group also contains FcepsilonRI which binds IgE with high affinity.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783  128 WLLLQTPQLVFLEGETITLRCHSWRNKLLNRISFFHNEKSVRYHHYSSNFSIPKANHSHSGDYYCKGSLGRTLHQSKPVT 207
Cdd:cd05753   1 WLLLQAPSAVVFEGEPLTLRCHGWKDKKVHKVTYYKDGKALKFSYENSNFSIPQATLSDSGSYHCSGTVRIKRRSSESVN 80

                ...
gi 6857783  208 ITV 210
Cdd:cd05753  81 ITV 83

Immunoglobulin domain; This domain contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783    128 WLLLQTPQLVFLEGETITLRCHSWRNKLLNrISFFHNEKSVRYHHyssNFSIPKANHSHSGDYYCKGSLGRTLHQSKPVT 207
Cdd:pfam13895   1 KPVLTPSPTVVTEGEPVTLTCSAPGNPPPS-YTWYKDGSAISSSP---NFFTLSVSAEDSGTYTCVARNGRGGKVSNPVE 76

                  ...
gi 6857783    208 ITV 210
Cdd:pfam13895  77 LTV 79

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783     134 PQLVFLEGETITLRCH---------SWRNKLLNRIsFFHNEKSVRYHHYSSNFSIPKANHSHSGDYYCKGSLGRTLHQSk 204
Cdd:smart00410   2 PSVTVKEGESVTLSCEasgspppevTWYKQGGKLL-AESGRFSVSRSGSTSTLTISNVTPEDSGTYTCAATNSSGSASS- 79

                   ....*.
gi 6857783     205 PVTITV 210
Cdd:smart00410  80 GTTLTV 85

Immunoglobulin domain; This domain contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 6857783     49 KLEPPWIQVLKEDTVTLTCEGTHNPGnSSTQWFHNGRSIRSQvQASYTFKATVNDSGEYRCQMEQTR---LSDPVDLGV 124
Cdd:pfam13895   3 VLTPSPTVVTEGEPVTLTCSAPGNPP-PSYTWYKDGSAISSS-PNFFTLSVSAEDSGTYTCVARNGRggkVSNPVELTV 79

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

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783      52 PPWIQVLKEDTVTLTCEGTHNPgNSSTQWFHNG----------RSIRSQVQASYTFK-ATVNDSGEYRCQ 110
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASGSP-PPEVTWYKQGgkllaesgrfSVSRSGSTSTLTISnVTPEDSGTYTCA 69

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

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783  130 LLQTPQLVFLEGETITLRCHSwRNKLLNRISFFHNEKSVRYHHYSS---NFSIPKANHSHSGDYYCKGSLGRTLHQ---- 202
Cdd:cd05711   4 LSAHPGPVVPSGENVTLQCHS-RIGFDRFILYKEGRSPLLQFHGSGfqaSFPLGPVTPAHAGTYRCYGSYNHSPYEwsap 82

                ....*...
gi 6857783  203 SKPVTITV 210
Cdd:cd05711  83 SDPLEIVV 90

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 6857783   48 VKLEPPWIQVLKEDTVTLTCEGTHNPGNSSTQWFHNGRSIRSQVQAS-------YTFKA-----TVNDSGE-YRCQMEQT 114
Cdd:cd20998   9 VTVYPTKTQPLEHHNLLVCSVSDFYPGNIEVRWFRNGKEEKTGIVSTglvrngdWTFQTlvmleTVPQSGEvYTCQVEHP 88

                ....*.
gi 6857783  115 RLSDPV 120
Cdd:cd20998  89 SLTDPV 94

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

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783   57 VLKEDTVTLTCEGTHnpgnsSTQWFH-----NGRSIRSQVQASYTFKA-------TVNDSGEYRCQ----MEQTRLSDPV 120
Cdd:cd16843  12 VPLGENVTIRCQGPP-----EAVLFQlykegNSLSQGTVREKEPQNKAefyiphmDRNHAGRYRCRyrsgTLWSEPSDPL 86

                ....
gi 6857783  121 DLGV 124
Cdd:cd16843  87 ELVV 90

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

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783   63 VTLTCEGTHNPGNSSTqWFHNGRSIRSQVQASYTF----------KATVNDSGEYRCQME 112
Cdd:cd00096   1 VTLTCSASGNPPPTIT-WYKNGKPLPPSSRDSRRSelgngtltisNVTLEDSGTYTCVAS 59

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

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 6857783   44 PKaVVKLEPPWIQVLKEDTVTLTCEGTHNPgNSSTQWFHNGRSI-----RSQV-QASYTFKATVN-DSGEYRC 109
Cdd:cd20978   1 PK-FIQKPEKNVVVKGGQDVTLPCQVTGVP-QPKITWLHNGKPLqgpmeRATVeDGTLTIINVQPeDTGYYGC 71

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 6857783    129 LLLQTPQLVFLEGETITLRCHSWRNKLlNRISFFHNEK--------SVRYHHYSSNFSIPKANHSHSGDYYCKGS 195
Cdd:pfam13927   4 ITVSPSSVTVREGETVTLTCEATGSPP-PTITWYKNGEpissgstrSRSLSGSNSTLTISNVTRSDAGTYTCVAS 77

Immunoglobulin (Ig)-like domain at the C-terminus of semaphorins; The members here are composed of the immunoglobulin (Ig)-like domain in semaphorins. Semaphorins are transmembrane protein that have important roles in a variety of tissues. Functionally, semaphorins were initially characterized for their importance in the development of the nervous system and in axonal guidance. Later they have been found to be important for the formation and functioning of the cardiovascular, endocrine, gastrointestinal, hepatic, immune, musculoskeletal, renal, reproductive, and respiratory systems. Semaphorins function through binding to their receptors and transmembrane semaphorins also serves as receptors themselves. Although molecular mechanism of semaphorins is poorly understood, the Ig-like domains may be involved in ligand binding or dimerization.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 6857783  134 PQLVFLEGETITLRCHSWRNklLNRISFFHNEKSVR-------YHHYSSNFSIPKANHSHSGDYYCKgSLGRTL-HQSKP 205
Cdd:cd04979   4 KQISVKEGDTVILSCSVKSN--NAPVTWIHNGKKVPryrsprlVLKTERGLLIRSAQEADAGVYECH-SGERVLgSTLRS 80

                ....*...
gi 6857783  206 VTITVQGP 213
Cdd:cd04979  81 VTLHVLER 88