C4b-binding protein binds C4b

Stable Identifier
Reaction [binding]
Homo sapiens
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The most abundant form of C4b-binding protein (C4BP) consists of seven alpha-chains (70kDa) and one beta-chain (45kDa) all linked by disulphide bonds to form a native protein with a molecular weight of 570kDa (Hilarp et al. 1989). Each alpha chain can bind C4b; it is not known whether full occupancy is necessary for subsequent events. The beta chain binds and inactivates Protein S, a component of the coagulation system. C4BP down-regulates complement activity in several ways: It binds to C4b thus inhibiting the formation of the classical pathway C3 convertase C4bC2a; it acts as a decay accelerating factor for existing convertases, probably by promoting dissociation of C2a; it is a cofactor in Factor I mediated C4b proteolysis.

Literature References
PubMed ID Title Journal Year
6222381 Visualization of human C4b-binding protein and its complexes with vitamin K-dependent protein S and complement protein C4b

Dahlback, B, Muller-Eberhard, HJ, Smith, CA

Proc Natl Acad Sci U S A 1983
670886 Human C4-binding protein. I. Isolation and characterization

Gigli, I, Ferreira, A, Scharfstein, J, Nussenzweig, V

J Exp Med 1978
6334079 Characterization of the interaction of human C4b-binding protein with physiological ligands

Dahlback, B, Ziccardi, RJ, Muller-Eberhard, HJ

J Biol Chem 1984
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