Anaphylatoxin, complement system domain (IPR001840)

Short name: Anaphylatoxn_comp_syst_dom

Overlapping homologous superfamilies

Domain relationships


Complement components C3, C4 and C5 are large glycoproteins that have important functions in the immune response and host defence [PMID: 1431125]. They have a wide variety of biological activities and are proteolytically activated by cleavage at a specific site, forming a- and b-fragments [PMID: 2777798]. A-fragments form distinct structural domains of approximately 76 amino acids, coded for by a single exon within the complement protein gene. The C3a, C4a and C5a components are referred to as anaphylatoxins [PMID: 2777798, PMID: 3081348]: they cause smooth muscle contraction, histamine release from mast cells, and enhanced vascular permeability [PMID: 3081348]; they also mediate chemotaxis, inflammation, and generation of cytotoxic oxygen radicals [PMID: 3081348]. The proteins are highly hydrophilic, with a mainly alpha-helical structure held together by 3 disulphide bridges [PMID: 3081348].

Some of the proteins in this group are responsible for the molecular basis of the blood group antigens, surface markers on the outside of the red blood cell membrane. Most of these markers are proteins, but some are carbohydrates attached to lipids or proteins [Reid M.E., Lomas-Francis C. The Blood Group Antigen FactsBook Academic Press, London / San Diego, (1997)]. Complement C4 belongs to the Chido/Rodgers blood group system and is associated with Ch1 to Ch6, WH, Rg1 and Rg2 antigens.

GO terms

Biological Process

GO:0006956 complement activation
GO:0006954 inflammatory response

Molecular Function

No terms assigned in this category.

Cellular Component

GO:0005576 extracellular region

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.