Complement component 4 binding protein beta chain (C4BPB)

Complement component 4 binding protein beta chain (C4BPB) is the beta subunit of the C4b-binding protein (C4BP), a key regulator of the classical and lectin pathways of complement activation in the innate immune system. In human blood, the main C4BP isoform is composed of seven alpha-chains and one unique beta-chain, forming a multimeric, spider-like protein with crucial roles in downregulating complement-mediated inflammation and injury. The beta chain specifically binds with high affinity to protein S, a vitamin K-dependent anticoagulant cofactor, linking C4BP to coagulation pathways. Through its cofactor activity with serine protease factor I, it accelerates the inactivation of the complement fragment C4b and the decay of C3 convertase complexes. C4BPB also contributes to the clearance of apoptotic and necrotic cells, interacts with various host and microbial molecules, and may be implicated in infectious disease pathogenesis and coagulation disorders[1][3][4][5].

Other names

C4b-binding protein beta chainC4BP beta chainComplement component 4 binding protein, beta chainC4BPC4BPB

Cofactor activity for serine protease factor I in inactivating C4b (and to a lesser extent C3b); Binding and regulation of protein S (vitamin K-dependent anticoagulant) affecting coagulation; Decay acceleration of C4bC2a complex (C3 convertase) in complement cascade[3][4][5]