Polymorphism of Ps (parotid size variant) and detection of a protein (PmS) related to the Pm (parotid middle band) system with genetic linkage of Ps and Pm to Gl, Db, and Pr genetic determinants

Abstract

Genetic polymorphism of the Ps (parotid size variant) proteins found in saliva is determined by autosomal inheritance of two expressed and one unexpressed allele. This hypothesis is supported by studies in 43 families including 153 children. Gene frequencies determined for 150 randomly collected salivas from whites and 101 randomly collected salivas from blacks are as follows: for whites, Ps ¹=0.598, Ps ²=0.101, Ps ⁰=0.301; for blacks, Ps ¹=0.185, Ps ²=0.126, and Ps ⁰=0.689. The electrophoretic polymorphism is manifested by apparent differences in molecular weights between Ps proteins. The Ps proteins are glycosylated and have an approximate isoelectric point of pI 8.1 as determined by isoelectric focusing in gels. We have also found in saliva the presence of a protein (PmS) which shows strong positive correlations with the presence of the smaller sized Pm (PmF) salivary protein described by Ikemoto et al. (1977). This suggested that PmS is probably part of the Pm protein polymorphic system. For randomly collected salivas from whites, the gene frequencies are PmF+=0.15 (N=140) and PmS+=0.12 (N=150). For randomly collected salivas from blacks, the gene frequency is PmS+=0.24 (N=101). The gene frequency of PmF+ was not determined. Family studies support autosomal inheritance of PmF and PmS proteins. There is strong evidence for linkage of Pm to the proline-rich protein (PPP) “region” (11 families, lod score at ϑ=0.01 is 7.64) and of Ps to the PPP “region” (13 families, lod score at ϑ=0.01 is 11.50). Protein products of six linked loci (Pr, Pa, Db, Ps, Pm, and Gl), when tested against rabbit anti-Gl antiserum, show immunological reactions of partial or complete identity with each other by double diffusion analysis.