Complement Component 8 beta Chain
Complement component 8 beta chain, encoded by C8B, links the C8 alpha-gamma subunit to the nascent membrane attack complex. During terminal pathway activation, C5b-7 exposes a binding site for the beta chain; once attached, beta positions the alpha-gamma pair so that the alpha chain can insert into the lipid bilayer and initiate C9 polymerization. Like the other C8 chains, beta contains a thrombospondin-type module alongside its membrane-attack-complex/perforin (MACPF) domain, a fold shared with perforin. C8 beta deficiency is a rare autosomal disorder that prevents pore formation and increases susceptibility to meningococcal and gonococcal infections.
