Porcine alpha-lactalbumin A and B.

The occurrence of the 'whey' protein, alpha-lactalbumin, in pig (Sus scrofus) milk samples from 904 sows is examined. A semi-discontinuous buffer system has been developed to detect the existence of genetic polymorphism. There are two homozygous variants, designated A and B. Both variants are isolated and it is shown by peptide and sequencing studies that the A variant differs from the B variant by having an Arg residue substituted for the Lys residue at the N-terminus of the molecule. The sequence of the first thirty residues is determined and compared with those of related alpha-lactalbumins.