Biosynthesis of pro-C3, a precursor of the third component of complement.

Abstract

A precursor of the 3rd component of complement, pro-C3, was detected in studies of cell-free synthesis and intracellularly in homogenates of liver tissue [guinea pig] cultures. The molecular weight of pro-C3 was indistinguishable from that of intact native C3 secreted in vitro by liver or peritoneal macrophages, but its structure was different. Pro-C3 is a single polypeptide chain, whereas C3 secreted by cells in culture consists of 2 polypeptide chains (MW 120,000 and 76,000) linked by disulfide bonds. [Rabbit antisera were used.].