Anaphylotoxin-like domain | |||||||||||
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![]() Structure of porcine C5adesArg.[1] | |||||||||||
Identifiers | |||||||||||
Symbol | ANATO | ||||||||||
Pfam | PF01821 | ||||||||||
InterPro | IPR000020 | ||||||||||
SMART | ANATO | ||||||||||
PROSITE | PDOC00906 | ||||||||||
SCOP2 | 1c5a / SCOPe / SUPFAM | ||||||||||
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Anaphylatoxins, or complement peptides, are fragments (C3a, C4a and C5a) that are produced as part of the activation of the complement system.[2] Complement components C3, C4 and C5 are large glycoproteins that have important functions in the immune response and host defense.[3] They have a wide variety of biological activities and are proteolytically activated by cleavage at a specific site, forming a- and b-fragments.[4] 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:[4][5] they cause smooth muscle contraction, vasodilation, histamine release from mast cells, and enhanced vascular permeability.[5] They also mediate chemotaxis, inflammation, and generation of cytotoxic oxygen radicals.[5] The proteins are highly hydrophilic, with a mainly alpha-helical structure held together by 3 disulfide bridges.[5]