Nucleotide sequence of gene PBI encoding a protein homologous to salivary proline-rich protein P-B

The nucleotide sequence of gene PBI, the putative translational product of which is homologous to salivary proline-rich protein P-B, has been determined. PBI is 6.4 kb long and contains 3 exons. PBI appears to code for the precursor of a proline-rich protein which we have designated P-B1. The P-B1 precursor is composed of 134 amino acid residues including 22 residues of signal sequence, 23 residues of N-terminal sequence, five repeating units of 13 to 14 residues and 22 residues of C-terminal sequence. The signal sequence of this precursor is identical with that of the P-B precursor. The N-terminal 61 residue sequence of P-B1 has homology of 75% with the whole sequence of P-B (57 residues), when deletion of 4 residues is taken into account. P-B1 is 55 residues longer than P-B.