Some Minor Components of Casein and Other Phosphoproteins in Milk. A Review

T-Casein and other minor proteins, tentatively designated TS-, R-, and S-casein, have been identified in unfractionaed casein by disc gel electrophoresis. T-Casein is polymorphic and like fl-easein it shows three variants of the A type and one B type. So far, no T-C casein has been observed. The A 2 and B polymorphs of T-and fi-casein show the same amino acid substitutions. The R-casein is found in A samples; the S-casein is associated with caseins typed B with respect to T-, flcasein. TS-Caseins occur in all samples and are polymorphic. This review will also discuss recent data on other minor caseins, the components of the proteosepeptone fraction, and the phosphoglycoprotein fraction of whey.