title: Porcine beta-lactoglobulin A and C. Occurrence, isolation and chemical properties.
abstract: The occurrence of the dominant 'whey' protein in samples of milk from 1180 sows is examined. It exhibits genetic polymorphism with some unusual features. Although immunologically different from bovine beta-lactoglobulin, it is shown by chemical studies of the isolated protein to be a beta-lactoglobulin. Two homozygous genetic variants, designated porcine beta-lactoglobulin A and C, are isolated and their amino acid compositions and peptide maps compared. It is shown that the C variant has +1 His, -1 Gln, and +1 Asp, -1 Glu, with respect to the A variant. These variants, containing ca. 162 residues per molecule, are considered in relationship to porcine beta-lactoglobulins isolated by other workers. The sequence of the first 50 residues is determined and compared with the sequence of the bovine protein. The sequences of ca. 70% of the remaining residues is proposed on the basis of the composition of tryptic peptides and assumed homology.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D005260:Female; D014644:Genetic Variation; D006720:Homozygote; D007782:Lactoglobulins / Q000235:genetics / Q000302:isolation & purification*; D008892:Milk / Q000032:analysis*; D010446:Peptide Fragments; D011110:Polymorphism, Genetic; D011247:Pregnancy; D013045:Species Specificity; D013552:Swine / Q000378:metabolism*
chemical_list: D007782:Lactoglobulins; D010446:Peptide Fragments