Immunoglobulin superfamily

The immunoglobulin superfamily is a group of proteins with some immunoglobulin- like amino acid sequences .

properties

The immunoglobulin superfamily is the most extensive group of surface proteins and soluble proteins (765 representatives in the human genome ) with different functions. The family is not exactly defined, but the representatives are characterized by a comparatively low homology of 20% to immunoglobulins (synonymous with antibodies), or have an immunoglobulin-like protein domain and are involved in extracellular protein-protein interactions . The immunoglobulin-like domain consists of 70 to 110 amino acids . It contains a certain protein fold (the immunoglobulin fold ) consisting of two stacked beta sheets , each made up of two antiparallel beta strands (B and F). By the hydrophobic amino acids and one disulfide bridge on the inside of the stacking leaflets formed. One end of the immunoglobulin fold contains the complementarity-determining region , which is responsible for the variable binding specificity of antibodies.

The typical immunoglobulin-like protein domain forms a rod-shaped structure. The immunoglobulin-like domains are divided into four groups: IgV (from variable ), IgC1 (from constant ), IgC2 or IgI (from intermediate ). IgV domains usually have 9 beta-sheet structures. IgC1 and IgC2 usually have 7.

Representatives of the immunoglobulin superfamily are immunoglobulins , killer cell immunoglobulin-like receptors , most Fc receptors , CD3 receptors , T cell receptors , myelin oligodendrocyte glycoprotein , B lymphocyte antigen CD19 , neural cell adhesion molecule 1 (CD56), CD31 , Siglec-3 (CD33), CD66a , CD66b , CD66c , CD66d , CD66e , CD66f , CD80 , CD86 , CD90 , CD96 and CD155 .

Groups of the immunoglobulin superfamily

function	Examples	description
Antibodies and receptors	Antibodies (synonymous with immunoglobulins): IgA IgD IgE IgG IgM T cell receptor
Antigen presentation	MHC I MHC II Beta-2 microglobulin
Co-receptors	CD4 CD8 CD19
Antigen receptor binding proteins	CD3 -γ, -δ and -ε CD79a and CD79b
Costimulators or Koinhibitoren	CD28 CD80 and CD86 (synonymous B7-1 and B7-2)
NK cell receptors	Killer Cell Immunoglobulin-like Receptors (KIR)
Leukocyte receptors	Leukocyte immunoglobulin-like receptors (LILR)
IgSF CAMs	NCAMs ICAM-1 CD2 Type IIa and Type IIb RPTPs
Cytokine receptors	Interleukin-1 receptor Colony stimulating factor 1 receptor
Growth Factor Receptors	Platelet-derived growth factor receptor (PDGFR) CD117 (SCFR, c-kit)
Receptor tyrosine kinases / tyrosine phosphatases	Tie-1 precursor Type IIa and Type IIb receptor protein tyrosine phosphatases (RPTPs), e.g. B. PTPRM , PTPRK , PTPRU , PTPRD , PTPRF
Immunoglobulin receptors	polymeric immunoglobulin receptor (PIGR) most of the Fc receptors
Other	CD147 CD90 CD7 IgSF-2 IgSF-3 Butyrophilins (Btn) Titin

Herpes viruses , smallpox viruses and adenoviruses form variants of various members of the immunoglobulin superfamily that inhibit immune evasion. Representatives were found in bacteria that were presumably ingested by horizontal gene transfer .

Individual evidence

1. ↑ Lander ES, Linton LM, Birren B, et al: Initial sequencing and analysis of the human genome . In: Nature . 409, No. 6822, February 2001, pp. 860-921. doi : 10.1038 / 35057062 . PMID 11237011 .
2. ^ ^{A b c} Peter Sonderegger: Ig Superfamily Molecules in the Nervous System. CRC Press, 2003, ISBN 978-0-203-30369-6 . P. IX, 1-3.
3. ↑ AN Barclay: Membrane proteins with immunoglobulin-like domains - a master superfamily of interaction molecules. In: Seminars in immunology. Volume 15, Number 4, August 2003, pp. 215-223, PMID 14690046 .
4. ↑ Y. Shimono, Y. Rikitake, K. Mandai, M. Mori, Y. Takai: Immunoglobulin superfamily receptors and adherens junctions. In: Sub-cellular biochemistry. Volume 60, 2012, pp. 137-170, doi : 10.1007 / 978-94-007-4186-7_7 , PMID 22674071 .
5. ↑ BD Gomperts, Ijsbrand M. Kramer, Peter ER Tatham: signal transduction . Academic Press, July 1, 2009, ISBN 978-0-12-369441-6 , p. 378 (accessed November 28, 2010).
6. ↑ Harpaz Y, Chothia C: Many of the immunoglobulin superfamily domains in cell adhesion molecules and surface receptors belong to a new structural set which is close to that containing variable domains . In: J. Mol. Biol. . 238, No. 4, May 1994, pp. 528-39. doi : 10.1006 / jmbi.1994.1312 . PMID 8176743 .
7. ↑ D. Farré, P. Martínez-Vicente, P. Engel, A. Angulo: Immunoglobulin superfamily members encoded by viruses and their multiple roles in immune evasion. In: European Journal of Immunology. Volume 47, number 5, May 2017, pp. 780-796, doi : 10.1002 / eji.201746984 , PMID 28383780 .
8. ↑ Bateman A, Eddy SR, Chothia C: Members of the immunoglobulin superfamily in bacteria . In: Protein Sci. . 5, No. 9, September 1996, pp. 1939-41. doi : 10.1002 / pro.5560050923 . PMID 8880921 . PMC 2143528 (free full text).