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

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 611987263  37 ALLTLEPPWVNVLREDNVTLKCEGFQTPGHDSIEWFHNGSAISFHQESYTIPAVNLKDSGEYQCRTEQTSLSNPVQLQV 115
Cdd:cd05752    1 AVVSLDPPWTTVFQGEKVTLTCQGFYSPEQNSTQWYHNGTLISSTSSSYRIVAATVNDSGEYRCQTQGSSLSDPVHLEV 79

First immunoglobulin (Ig)-like domain of Fcgamma-receptors (FcgammaRs), and similar domains; The members here are composed of the first 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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 611987263  37 ALLTLEPPWVNVLREDNVTLKCEGFQTPGHDSIEWFHNGSAISFHQESYTIPAVNLKDSGEYQCRTEQTSLSNPVQLQV 115
Cdd:cd05752    1 AVVSLDPPWTTVFQGEKVTLTCQGFYSPEQNSTQWYHNGTLISSTSSSYRIVAATVNDSGEYRCQTQGSSLSDPVHLEV 79

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 611987263   34 PPKalLTLEPPWVNVLREDNVTLKCEGFQTPgHDSIEWFHNGSAI----------SFHQESYTIPAVNLKDSGEYQCR 101
Cdd:pfam13927   1 KPV--ITVSPSSVTVREGETVTLTCEATGSP-PPTITWYKNGEPIssgstrsrslSGSNSTLTISNVTRSDAGTYTCV 75

First immunoglobulin (Ig)-like domain of Fcgamma-receptors (FcgammaRs), and similar domains; The members here are composed of the first 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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 611987263  37 ALLTLEPPWVNVLREDNVTLKCEGFQTPGHDSIEWFHNGSAISFHQESYTIPAVNLKDSGEYQCRTEQTSLSNPVQLQV 115
Cdd:cd05752    1 AVVSLDPPWTTVFQGEKVTLTCQGFYSPEQNSTQWYHNGTLISSTSSSYRIVAATVNDSGEYRCQTQGSSLSDPVHLEV 79

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 611987263   34 PPKalLTLEPPWVNVLREDNVTLKCEGFQTPgHDSIEWFHNGSAI----------SFHQESYTIPAVNLKDSGEYQCR 101
Cdd:pfam13927   1 KPV--ITVSPSSVTVREGETVTLTCEATGSP-PPTITWYKNGEPIssgstrsrslSGSNSTLTISNVTRSDAGTYTCV 75

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 611987263  36 KALLTLEPPWVnVLREDNVTLKCEGfqTPGHDSIEWFHNGSAISFHQE---------SYTIPAVNLKDSGEYQCR----T 102
Cdd:cd16843    1 KPFLSAEPSSV-VPLGENVTIRCQG--PPEAVLFQLYKEGNSLSQGTVrekepqnkaEFYIPHMDRNHAGRYRCRyrsgT 77

                         90
                 ....*....|...
gi 611987263 103 EQTSLSNPVQLQV 115
Cdd:cd16843   78 LWSEPSDPLELVV 90

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 611987263    43 PPWVNVLREDNVTLKCEGFQTPgHDSIEWFHNGSAI-----------SFHQESYTIPAVNLKDSGEYQC--RTEQTSLSN 109
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASGSP-PPEVTWYKQGGKLlaesgrfsvsrSGSTSTLTISNVTPEDSGTYTCaaTNSSGSASS 79

                   ....*.
gi 611987263   110 PVQLQV 115
Cdd:smart00410  80 GTTLTV 85

T-cell surface glycoprotein CD3 delta chain; This is an immunoglobulin-like domain. It is found on the T-cell surface glycoprotein CD3 delta chain. CD3delta and CD3epsilon complex together as part of the T-cell receptor complex.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 611987263   51 EDNVTLKCEGfqtpGHDSIEWFHNGSAISFH-QESYTIPAVNLKDSGEYQCRTEQTSlSNPVQL 113
Cdd:pfam16680   1 DGKVLLTCNS----SSKSITWLKDGKGIKSTnTKTLDLGKFSEDPRGLYQCQGEKKK-SSTLQV 59

Immunoglobulin (Ig)-like domain of human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) domains 2, 4, and 6, and similar domains; The members here are composed of the second, fourth, and sixth immunoglobulin (Ig)-like domains in human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) protein subfamily. The CEA family is a group of anchored or secreted glycoproteins expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions; it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two [D1, D4] or four [D1-D4] Ig-like domains on the cell surface.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 611987263  51 EDNVTLKCEGfQTPGhDSIEWFHNGSAISFHQE--------SYTIPAVNLKDSGEYQCRTEQ---TSLSNPVQLQV 115
Cdd:cd05740   15 KDAVTLTCEP-ETQN-TSYLWWFNGQSLPVTPRltlsngnrTLTLLNVTREDAGAYQCEISNpvsANRSDPVTLDV 88

Immunoglobulin I-set domain;

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|
gi 611987263   54 VTLKCE--GFQTPghdSIEWFHNGSAIS------FHQESY----TIPAVNLKDSGEYQCR 101
Cdd:pfam07679  18 ARFTCTvtGTPDP---EVSWFKDGQPLRssdrfkVTYEGGtytlTISNVQPDDSGKYTCV 74