C4BPA Gene: Complement Component 4 Binding Protein Alpha - Function, Mutations & Disease

C4BPA encodes the alpha chain of complement component 4 binding protein (C4BP), a multimeric protein that regulates the classical and lectin pathways of complement activation. C4BP binds complement component C4b, acting as a cofactor for factor I-mediated cleavage of C4b, thereby preventing formation of the C3 convertase and controlling complement cascade. The gene is located on chromosome 1q32.2 within the regulators of complement activation (RCA) gene cluster. C4BPA is primarily expressed in the liver and circulates in plasma. Mutations and polymorphisms in C4BPA have been associated with thrombophilia, autoimmune diseases, and infections.

Tissue Expression

Cell Line Expression

Hotspot Mutations

Mutation functional classification

• Complement cascade (Reactome: R-HSA-166658)

• Regulation of complement activation (KEGG: hsa04610)

The C4BPA protein is a 597-amino acid alpha chain that assembles into a multimeric complex (C4BP) with beta chains (C4BPB). The alpha chain contains eight complement control protein (CCP) domains that mediate C4b binding and factor I cofactor activity. C4BP circulates in plasma as a high-molecular-weight complex and is a key regulator of the classical complement pathway, preventing excessive inflammation and tissue damage. Post-translational modifications include N-glycosylation and disulfide bond formation.