C4BPA

This gene encodes a member of a superfamily of proteins composed predominantly of tandemly arrayed short consensus repeats of approximately 60 amino acids. Along with a single, unique beta-chain, seven identical alpha-chains encoded by this gene assemble into the predominant isoform of C4b-binding protein, a multimeric protein that controls activation of the complement cascade through the classical pathway. The genes encoding both alpha and beta chains are located adjacent to each other on human chromosome 1 in the regulator of complement activation gene cluster. Two pseudogenes of this gene are also found in the cluster.

Full Name

complement component 4 binding protein alpha

Function

Controls the classical pathway of complement activation. It binds as a cofactor to C3b/C4b inactivator (C3bINA), which then hydrolyzes the complement fragment C4b. It also accelerates the degradation of the C4bC2a complex (C3 convertase) by dissociating the complement fragment C2a. Alpha chain binds C4b. It interacts also with anticoagulant protein S and with serum amyloid P component.

Biological Process

Complement activation, classical pathway Source: UniProtKB-KW
Innate immune response Source: UniProtKB-KW
Negative regulation of complement activation, classical pathway Source: BHF-UCL
Positive regulation of protein catabolic process Source: BHF-UCL
Regulation of complement activation Source: Reactome
Regulation of opsonization Source: BHF-UCL
Response to symbiotic bacterium Source: BHF-UCL

Cellular Location

Secreted