The primary structure of the fourth component of human complement (C4)-C-terminal peptides

C-terminal CNBr peptides of the three polypeptide chains of C4 were obtained and sequenced. These results supplement previously obtained data, notably the protein sequence derived from cDNA sequencing of pro-C4 (Belt KT, Carroll MC & Porter RR (1984) Cell36, 907–914) and the N-terminal sequences of the three polypeptides (Gigli I, von Zabern I & Porter RR (1977) Biochem. J.165, 439–446), to define the complete primary structure of the plasma form of C4. The β (656 residues), α (748 residues), and γ (291 residues) chains are found in positions 1–656, 661–1408, and 1435–1725 in the pro-C4 molecule.