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 25777657  44 EVNTSWPVKMATNAVLCCPPIALRNLIIITWEIILRGQPSCTKAYKKETNETkETNCTDERITWVSRPDQNSDLQIRTVA 123
Cdd:cd20985   2 EVNTTVSVQMGTKALLCCFSIPLTKAVLITWIIKLRGQPSCTIAYKVDTKET-ETSCLDRNITWASTPDHSPDLQISAVA 80

                        90       100
                ....*....|....*....|....*..
gi 25777657 124 ITHDGYYRCIMVTPDGNFHRGYHLQVL 150
Cdd:cd20985  81 LQHEGTYSCEIVTPEGNFQKVYDLQVL 107

Immunoglobulin Variable domain of cell surface glycoprotein CD200 receptor and similar proteins; The members here are composed of the immunoglobulin variable (IgV) domain of cell surface glycoprotein CD200 receptor and similar proteins. CD200 (also known as OX2) is a widely distributed membrane glycoprotein that regulates myeloid cell activity through its interaction with an inhibitory receptor (CD200R). CD200-CD200R interactions are involved in the control of myeloid cellular function. In the mouse, several CD200R-related genes have been identified, including CD200RL (for receptor like), CD200R1, and CD200R2. While CD200 gives good binding to CD200R, it does not bind CD200RLa, CD200RLb, CD200RLc, or CD200RLe. For instance, CD200RLa has a 50-fold lower binding affinity to CD200, although CD200RLa shares a high amino acid sequence identity with CD200R in the V-like domain. Furthermore, the CD200-CD200R regulatory interactions provide an attractive target for immunomodulation, because its manipulation can provoke either immune tolerance or autoimmune diseases.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 25777657  44 EVNTSWPVKMATNAVLCCPPIALRNLIIITWEIILRGQPSCTKAYKKETNETkETNCTDERITWVSRPDQNSDLQIRTVA 123
Cdd:cd20985   2 EVNTTVSVQMGTKALLCCFSIPLTKAVLITWIIKLRGQPSCTIAYKVDTKET-ETSCLDRNITWASTPDHSPDLQISAVA 80

                        90       100
                ....*....|....*....|....*..
gi 25777657 124 ITHDGYYRCIMVTPDGNFHRGYHLQVL 150
Cdd:cd20985  81 LQHEGTYSCEIVTPEGNFQKVYDLQVL 107

Immunoglobulin Variable domain of cell surface glycoprotein CD200 receptor and similar proteins; The members here are composed of the immunoglobulin variable (IgV) domain of cell surface glycoprotein CD200 receptor and similar proteins. CD200 (also known as OX2) is a widely distributed membrane glycoprotein that regulates myeloid cell activity through its interaction with an inhibitory receptor (CD200R). CD200-CD200R interactions are involved in the control of myeloid cellular function. In the mouse, several CD200R-related genes have been identified, including CD200RL (for receptor like), CD200R1, and CD200R2. While CD200 gives good binding to CD200R, it does not bind CD200RLa, CD200RLb, CD200RLc, or CD200RLe. For instance, CD200RLa has a 50-fold lower binding affinity to CD200, although CD200RLa shares a high amino acid sequence identity with CD200R in the V-like domain. Furthermore, the CD200-CD200R regulatory interactions provide an attractive target for immunomodulation, because its manipulation can provoke either immune tolerance or autoimmune diseases.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 25777657  44 EVNTSWPVKMATNAVLCCPPIALRNLIIITWEIILRGQPSCTKAYKKETNETkETNCTDERITWVSRPDQNSDLQIRTVA 123
Cdd:cd20985   2 EVNTTVSVQMGTKALLCCFSIPLTKAVLITWIIKLRGQPSCTIAYKVDTKET-ETSCLDRNITWASTPDHSPDLQISAVA 80

                        90       100
                ....*....|....*....|....*..
gi 25777657 124 ITHDGYYRCIMVTPDGNFHRGYHLQVL 150
Cdd:cd20985  81 LQHEGTYSCEIVTPEGNFQKVYDLQVL 107