Purification and characterization of the eighth and ninth components of carp complement

Complement components corresponding to mammalian C8 and C9 were isolated from carp (Cyprinus carpio) serum. Carp C8 (M(r) 146,000) proved to be a gamma-globulin composed of three polypeptide chains (alpha-chain, M(r) 62,000; beta-chain, M(r) 62,000; gamma-chain, M(r) 22,000). The alpha-chain was disulfide-linked to the gamma-chain and the beta-chain was non-covalently associated with the alpha-gamma chain, in fair agreement with mammalian C8. However, the N-terminal amino acid sequences of the three subunits showed no homology with those of human C8. Carp C9 was an alpha-globulin composed of a single polypeptide (M(r) 91,000) and the N-terminus was blocked. Carp serum depleted of C8 did not hemolyse either carp antibody-sensitized sheep erythrocytes or non-sensitized rabbit erythrocytes, while C9-depleted carp serum did not hemolyse the former, but did hemolyse the latter target cells, as in the case of C9-depleted human serum.