Bovine serum transferrin phenotypes AA, D1D1, D2D2, EE: Their carbohydrate compositions and electrophoretic multiplicity

Abstract

Samples of homozygous bovine serum transferrins have been prepared and their purity has been ascertained by immunological techniques and electrophoretic analysis in SDS. Measurements of carbohydrate composition show that no significant differences exist among the phenotype variants AA, D1D1, D2D2, and EE. Chromatography of transferrin AA on DEAE-cellulose separated four subfractions, each of which corresponded well with one band obtained by polyacrylamide gel electrophoresis. Carbohydrate analyses of the individual subfractions did not show significant differences in sialic acid, hexose, or hexosamine contents. After desialylation with neuraminidase, each subfraction was converted to a major band and a minor band on gel electrophoresis. From the relative band positions of the desialylated transferrins, it was concluded that possession of sialyl residued by bovine transferrin is not the primary cause of electrophoretic multiplicity. Rather, sialic acid masks an underlying heterogeneity which most likely resides within the polypeptide chain. Further characterization of this heterogeneity will best be undertaken with the isolated asialotransferrin subfractions.

Nature of the heterogeneity within genetic variants of bovine serum transferrin

“…This is in accord with the previous observations of Stratil & Spooner (1971) on their transfemn components from normal adult cattle. Neither work appears to be in agreement with the results of Hatton et al (1977). We believe that our components I, 11, I11 and IV correspond respectively to components 2a, 2b, 3a and 3b of Stratil & Spooner.…”

“…However, Spooner and co-workers were unable to explain the difference between the a and b components of any given pair of bands, and concluded it did not reside in sialic acid differences. Subsequently, Hatton et al (1977) claimed that there were no differences in carbohydrate content (sialic acid, hexose, hexosamine) for the components of a given homozygous variant and that all the heterogeneity must reside other than in the carbohydrate moiety. On the contrary, we conclude that the results of Spooner and collaborators with respect to sialic acid are in accord with our observations and conclude in the present work that the difference between the components within a given pair of a and b bands is due to a scission in the peptide chain of the b band component.…”

Interaction of transferrin and its iron-binding fragments with heparin.

“…Bovine transferrin (bTf) was purified by a published method [11]. As bTf is the product of four allelic genes, and thus exhibits anionic heterogeneity, single anionic species were used with one additional component as a minor contaminant.…”