Nucleotide sequence analysis of a proline-rich protein cDNA and peptide homologies of rat and human proline-rich proteins.

Plasmids containing cDNAs for proline-rich proteins have been isolated from a cDNA library prepared from parotid glands of isoproterenol-treated rats. The nucleotide sequence of one of these cDNAs (pRP33) has been determined, and it encodes an acidic proline-rich protein. The N-terminal 13 amino acids are highly hydrophobic and may be part of a signal peptide. The next 66 amino acids constitute an acidic domain which is interrupted by a short (8 residue) basic region. The sequence beginning at proline 80 contains six tandemly repeated regions of 18 to 19 amino acids in length with the prototype sequence PPPQGGPQXPPQPGXPQG. Two pairs of these repeats (amino acid residues 116 to 152 and 153 to 189) are 93% homologous in nucleotide sequence. The high homology in both nucleotide and amino acid sequences in the repeat region suggests that this protein may have evolved by duplication of internal portions of a progenitor gene.