Amino terminal sequence, processing, and biological activity of porcine pre-alpha-lactalbumin.

Polyadenylated RNAs isolated from bound polysomes of a lactating sow's mammary gland, were translated in a cell-free system and in vitro synthesized alpha-lactalbumin was immunoprecipitated and radiosequenced. The translation product was found to contain an amino terminal extension of 19 amino acid residues, very similar to its ovine counterpart, that was selectively removed when translation was carried out in the presence of rabbit mammary microsomal membranes. Assays of porcine pre-alpha-lactalbumin for activity on galactosyltransferase showed that the preprotein can also interact with and modify the specificity of the enzyme, as indicated by de novo synthesis of lactose.

Cell-free synthesis, proteolytic processing, core glycosylation, and amino terminal sequence of rabbit pre-alpha-lactalbumin.

Two different forms of alpha-lactalbumin were isolated from rabbit milk and partially characterized. The major and the minor species had apparent molecular weights of 18000 and 14000, respectively, according to their electrophoretic mobilities on SDS polyacrylamide gels. Analyses of their amino acid compositions and amino-and carboxy-terminal sequences did not reveal any difference, but sugar analysis showed the occurrence of carbohydrates in the major species.

N-terminal sequences of uteroglobin and its precursor.

Translation of uteroglobin mRNA in wheat-germ extract has yielded a precursor protein (pre-uteroglobin) containing an N-terminal extension of 21 amino acid residues. The sequence of this extension and that of the 50 N-terminal amino acid residues of uteroglobin have been determined.