Human complement component C8 Molecular basis of the β-chain polymorphism

The β-chain of human complement component C8 exhibits a structural genetic polymorphism: using isoelectric focusing two major allotypes can be identified (C8B B (‘basic’) and C8B A (‘acidic’)). In the present report we describe a sequence polymorphism of the C8B gene (codon 63: AGA → GGA) and demonstrate that the resulting amino acid substitution (Arg → Gly) consistently differentiates between the two common charge variants of the C8β chain; the C8B B allotype is characterized by an Arg and the C8B A allotype by a Gly residue in position 63 of the C8β polypeptide chain.