Multiple forms of the proline-rich polypeptide (PRP) bound to rat prostatic binding protein.

The proline-rich polypeptide, that is bound to rat prostatic binding protein displays a marked heterogeneity on isoelectric focusing, with major bands at pH 7.6 and pH 6.9. The same complex pattern is obtained for PRP prepared from prostates of individual rats from several strains. Using carboxymethylcellulose chromatography 6 different forms of PRP can be separated. Five of them have the same size (MW : 4000) and respectively glycine and lysine as N- and C-terminal amino acid. Their amino acid composition suggests that these forms differ by internal substitution respectively of aspartic acid and glycine and of proline and histidine. The sixth form (MW : 3500) lacks several amino acids at its N-terminal.