Tissue distribution and nucleotide sequence of bovine mRNA for salivary proline-rich protein P-B

The tissue distribution of P-B was investigated to obtain information on the physiological significance of this proline-rich protein. To design primers and probes for a tissue distribution analysis, a polymerase chain reaction (PCR)-based cloning of bovine P-B cDNA was performed using tooth germ and the nucleotide sequence was determined. The cloned bovine P-B cDNA was composed of 356 bp and included the region corresponding to the mature P-B protein and part of the 3′ non-coding sequence. This part of the sequence is identical to the corresponding region of human P-B cDNA from the submaxillary gland. DNA corresponding to the P-B mRNA was amplified by PCR using cDNAs from various bovine tissues including tooth germ, submaxillary gland, parotid gland, lachrymal gland, heart, liver, stomach, pancreas, spleen, kidney, adrenal, and ovary. A quantitative analysis indicated the heart, submaxillary gland, tooth germ and kidney to be major sites of P-B expression. The ubiquitous distribution of P-B mRNA among bovine tissues together with findings of the presence of genes hybridizable with a DNA probe for P-B among species such as human, bovine, rat, mouse, and yeast as reported previously suggested a fundamental physiological role for this protein.