Structural studies on rat prostatic binding protein. The primary structure of its glycosylated component C3

The amino acid sequence of the glycosylated component C3 of rat prostatic binding protein has been determined. The peptides obtained by digestion of the S-carboxamidomethylated or S-aminoethylated glycoprotein with trypsin and Staphylococcus aureus protease were sequenced by manual Edman degradation. The alignment of the fragments was further established with overlapping peptides obtained by enzymic hydrolysis of the modified protein with chymotrypsin and thermolysin, and by chemical cleavage with cyanogen bromide. The glycopeptide C3 contains 77 amino acids corresponding to a molecular weight of 8653. the oligosaccharide chain is attached to the peptide by an N-glycosidic bond to asparagine-17. C3 is an acidic polypeptide due to the presence of ten acidic residues; its three cysteine residues are located at both extremities and in the middle of the molecule.