Genetics of Salivary Protein Polymorphisms

Abstract

Human salivary PRPs are detennined by six closely linked genes on chromosome 12pl3.2. The many PRPs show complex electrophoretic patterns that differ between individuals and reflect numerous genetic polymorphisms. Frequent length and null polymorphisms are common among PRPs. Common themes emerge as a background for these PRP polymorphisms. First, posttranslational proteolysis occurs with double-banded patterns among acidic PRPs and the generation of numerous basic PRPs derived from precursor proteins. Specific mutations may interfere with proteolysis, preventing generation of double-banded acidic PRPs (as with the Pa protein) or of small basic PRPs from precursor proteins (as with Pm proteins). Second, single cysteine substitutions in PRPs (Pa from PRHI and Gl 8 from PRB3) may lead to disulfide bonded homodimers as well as heterodimers with salivary peroxidase. Third, frequent homologous and unequal crossing-over within the PRP gene cluster leads to frequent protein size-variants (intragenic events as with the Gl protein variants) and the generation of the PRB2/1 fusion gene (intergenic event) with deletion of the PRB1 coding region and absence of multiple PRBI coded proteins (Ps, Pm, Pe) in PRB2/1 homozygotes. Fourth, null mutations may also be produced (as with PsO and Gl 0) by single nucleotide changes.

Acinar Cells Are Target Cells for Androgens in Mouse Submandibular Glands

“…Proline-rich proteins are abundant in the saliva, well-characterized in humans, rats and mice (Ann and Carlson 1985;Clements et al 1985;Carlson 1988;Lin and Ann 1991;Azen 1993;Kim et al 1993). They contain a repeat segment rich in proline.…”

Does Variability in Salivary Protein Concentrations Influence Oral Microbial Ecology and Oral Health?

“…For example, the aPRP family includes two loci, with three common alleles at the first locus and two at the second. This results in a wide range of phenotypes (Azen, 1993;Hay et al, 1994). Although aPRP polymorphism has been known for many years, it has only recently become possible to quantify products of individual alleles (Hay et al, 1994).…”

“…Many salivary proteins are products of multiple gene families, and multiple alleles may be present at each of those loci (Azen, 1993;Meisler and Ting, 1993;Saitoh and Isemura, 1993). For example, the aPRP family includes two loci, with three common alleles at the first locus and two at the second.…”

“…Proline-rich proteins (PRP) are a multi-gene family of acinar proteins which include proline-rich glycoprotein (PRG) and multiple isoforms of acidic (aPRP) and basic (bPRP) proline-rich proteins (Azen, 1993). PRP contain proline in distinctive repeats that have some homology with collagen Lamkin and Oppenheim, 1993).…”

Possible Release of an ArgGlyArgProGln Pentapeptide with Innate Immunity Properties from Acidic Proline-Rich Proteins by Proteolytic Activity in Commensal Streptococcus and Actinomyces Species

“…Streptococcus and Actinomyces strains (14,17) were grown at 37°C for 18 h in 5 ml of Trypticase soy bean glucose limiting broth (1.7% peptone, 0.3% soy peptone, 0.15% yeast extract, 12.5 mmol of glucose/liter, and 12.5 mmol of NH 4 PRP degradation was assayed by mixing equal volumes (300 l) of protein (0.6 mg/ml) and bacteria (2 ϫ 10 9 cells/ml), both dissolved in M-DIL buffer, followed by incubation at 37°C for various times (15 min, 4 h, 20 h, and 1 week). After pelleting (17,000 ϫ g for 10 min) of bacterial cells, the supernatants were aliquoted, lyophilized, and stored at Ϫ80°C prior to native alkaline polyacrylamide gel electrophoresis (PAGE) and densitometric analyses as previously described except for the use of Tris-glycine 7.5% Ready gels (Bio-Rad) (7).…”