| Primary Identifier | IPR018081 | Type | Homologous_superfamily |
| Short Name | Anaphylatoxin_comp_syst |
| description | Complement components C3, C4 and C5 are large glycoproteins that have important functions in the immune response and host defence []. They have a wide variety of biological activities and are proteolytically activated by cleavage at a specific site, forming a- and b-fragments []. 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 [, ]: they cause smooth muscle contraction, histamine release from mast cells, and enhanced vascular permeability []. They also mediate chemotaxis, inflammation, and generation of cytotoxic oxygen radicals []. The proteins are highly hydrophilic, with a mainly α-helical structure held together by 3 disulphide bridges []. |
