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        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 31542804  41 AVVKRDPPWIQVLKDDTVTLTCEGTHNPGNSSTQWFHNQssTWGQVQASYTF--KATVNDSGEYRCRMAHTSLSDPVHLE 118
Cdd:cd05752   1 AVVSLDPPWTTVFQGEKVTLTCQGFYSPEQNSTQWYHNG--TLISSTSSSYRivAATVNDSGEYRCQTQGSSLSDPVHLE 78

                .
gi 31542804 119 V 119
Cdd:cd05752  79 V 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        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 31542804  41 AVVKRDPPWIQVLKDDTVTLTCEGTHNPGNSSTQWFHNQssTWGQVQASYTF--KATVNDSGEYRCRMAHTSLSDPVHLE 118
Cdd:cd05752   1 AVVSLDPPWTTVFQGEKVTLTCQGFYSPEQNSTQWYHNG--TLISSTSSSYRivAATVNDSGEYRCQTQGSSLSDPVHLE 78

                .
gi 31542804 119 V 119
Cdd:cd05752  79 V 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 31542804    129 PQLVFLEGERITLRCHGWKSIQlARISFLQNGE---------FVSFHPYNVSYSISNANHSHSGDYYCKAYLGRTEhVSK 199
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPP-PEVTWYKQGGkllaesgrfSVSRSGSTSTLTISNVTPEDSGTYTCAATNSSGS-ASS 79

                   ....*.
gi 31542804    200 PVTITV 205
Cdd:smart00410  80 GTTLTV 85

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 31542804    47 PPWIQVLKDDTVTLTCEGTHNPgNSSTQWFHNQSSTWGQVQASYTF----------KATVNDSGEYRCR 105
Cdd:pfam13927   8 PSSVTVREGETVTLTCEATGSP-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        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 31542804  41 AVVKRDPPWIQVLKDDTVTLTCEGTHNPGNSSTQWFHNQssTWGQVQASYTF--KATVNDSGEYRCRMAHTSLSDPVHLE 118
Cdd:cd05752   1 AVVSLDPPWTTVFQGEKVTLTCQGFYSPEQNSTQWYHNG--TLISSTSSSYRivAATVNDSGEYRCQTQGSSLSDPVHLE 78

                .
gi 31542804 119 V 119
Cdd:cd05752  79 V 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        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 31542804 124 LLLQTPQLVFLEGERITLRCHGWKSIQLARISFLQNGEFVSFHPynVSYSISNANHSHSGDYYCKAYLGrteHVSKPVTI 203
Cdd:cd05752   3 VSLDPPWTTVFQGEKVTLTCQGFYSPEQNSTQWYHNGTLISSTS--SSYRIVAATVNDSGEYRCQTQGS---SLSDPVHL 77

                ..
gi 31542804 204 TV 205
Cdd:cd05752  78 EV 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 31542804     47 PPWIQVLKDDTVTLTCEGTHNPgNSSTQWFHNQ----------SSTWGQVQASYTFK-ATVNDSGEYRCRM--AHTSLSD 113
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASGSP-PPEVTWYKQGgkllaesgrfSVSRSGSTSTLTISnVTPEDSGTYTCAAtnSSGSASS 79

                   ....*.
gi 31542804    114 PVHLEV 119
Cdd:smart00410  80 GTTLTV 85

Immunoglobulin domain; Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include antibodies, the giant muscle kinase titin and receptor tyrosine kinases. Immunoglobulin-like domains may be involved in protein-protein and protein-ligand interactions.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 31542804    47 PPWIQVLKDDTVTLTCEGTHNPGNSSTQWFHNQS----------STWGQVQASYTF-KATVNDSGEYRCRMAHTSLSDP 114
Cdd:pfam00047   3 PPTVTVLEGDSATLTCSASTGSPGPDVTWSKEGGtlieslkvkhDNGRTTQSSLLIsNVTKEDAGTYTCVVNNPGGSAT 81

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 31542804   124 LLLQTPQLVFLEGERITLRCHGwKSIQLARISFLQNGE--------FVSFHPYNVSYSISNANHSHSGDYYCKA 189
Cdd:pfam13927   4 ITVSPSSVTVREGETVTLTCEA-TGSPPPTITWYKNGEpissgstrSRSLSGSNSTLTISNVTRSDAGTYTCVA 76

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 31542804 128 TPQLVFLEGERITLRCHGwkSIQLARISFLQNGEFVSFHPYN-------VSYSISNANHSHSGDYYCKAYLGRTEHV-SK 199
Cdd:cd16843   7 EPSSVVPLGENVTIRCQG--PPEAVLFQLYKEGNSLSQGTVRekepqnkAEFYIPHMDRNHAGRYRCRYRSGTLWSEpSD 84

                ....*.
gi 31542804 200 PVTITV 205
Cdd:cd16843  85 PLELVV 90