Human parotid size polymorphism (Ps): characterization of two allelic products, Ps 1 and 2, by limited proteolysis.

The allelically determined human salivary proteins, Ps 1 and 2, were purified on sodium dodecyl sulfate gels, eluted, and compared by limited proteolysis with Streptomyces griseus protease VI, Bacillus subtilis protease VII, and Staphylococcus aureus protease V8. Prior dansylation of the Ps isoproteins facilitated visualization of the peptides. Digestion patterns indicate considerable homology between the Ps isoproteins and support the conclusion [Azen, A. E., and Denniston, C. (1980). Biochem. Genet. 18:483] that there is an actual molecular weight difference between them. Further, the results suggest that this difference owes to an extension of the Ps 2 chain at one of its ends.