STRUCTURAL STUDIES ON RAT PROSTATIC BINDING PROTEIN: THE PRIKARY STRUCTURE OF COMPONENT C2 FROM SUBUNIT S

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Abstract
The amino acid sequence of component C2, the polypeptide specific for subunit S of prostatic binding protein, the major secretory glycoprotein of the rat ventral prostate, was determined. Its structure was established using the manual Edman degradation on the most relevant fragments obtained by enzymatic digestion of the S-carboxamidomethylated component C2 and the native subunit S and by chemical cleavage of the remaining undigestible cores with cyanogen bromide. Component C2 contains 92 amino acids corresponding to a MW of 10,619. It is a slightly acidic polypeptide in which the acidic and basic residues are unevenly distributed. The N terminus is blocked and 3 cysteine residues are almost evenly distributed over the peptide chain. A highly polar region is found in position 23-34 and 2 hydrophobic segments are located in the C-terminal part of the molecule. Component C2 is compared with component C1 of subunit F and their high sequence homology reveals an evolutionary relationship.