Acidic Salivary Proline Rich Phosphoprotein 1 (PRH1)

According to the hypothesis of Maeda, the 3 acidic PRPs, Db, Pa, and PIF, are coded for by alleles at a single locus rather than by 3 discrete loci. The hypothesis is based on DNA studies which suggest that 6 loci control the synthesis of the PRPs. Genes at 2 of these loci, PRH1 and PRH2 (so named because they contain repeated cleavage sites for the restriction enzyme HaeIII), code for the acidic PRPs. Genes at the remaining 4 loci (PRB1, PRB2, PRB3, and PRB4) contain regions that strongly hybridize to a probe with repeated BstNI sites; they probably code for the basic and glycosylated PRPs. This hypothesis of 6 loci forming 2 gene subfamilies contrasts with that based on protein polymorphisms in families that suggest 13 loci with 11 common null alleles.