Purification and Characterization of Rat α-Lactalbumins: Apparent Genetic Variants

Abstract

Rat .alpha.-lactalbumin, from the milk of Fischer 344(CDF) rats, was isolated and purified by a combination of gel filtration and diethylaminoethyl-cellulose ion exchange chromatography. Three electrophoretically distinct proteins had .alpha.-lactalbumin activity. At least 2 of the 3 forms were revealed by staining to be glycoproteins. The low MW protein fraction from the wheys of 2 additional strains of laboratory rat were compared to ascertain whether the composition of this fraction was common in the divergent strains. Outbred Wistar and Long-Evans dams yielded wheys containing up to 6 forms of .alpha.-lactalbumin. Either 1 or both of 2 groups of 3 .alpha.-lactalbumins were in a given milk sample. The 2 groups of 3 .alpha.-lactalbumins appear to represent 2 genetic variatns upon which is imposed a polymorphic character. All forms of .alpha.-lactalbumin, within and between strains, were immunologically identical.