Phylogenetical and ontogenetical studies on the molecular weight heterogeneity of bovine serum transferrin.

Antitransferrin (Tf) rabbit serum was highly specific: it reacted with Tfs of ruminants, such as European breeds and Zebu breeds of cattle, Bali cattle, banteng, swamp and river types of water buffalo, anoa, goat, sheep, deer, antelope, camel, and giraffe, but did not react with serum of other non-ruminant species, such as pig, wild boar, hippopotamus, horse, rabbit, rat, chicken, etc. Electrophoresis of Tf and immunoglobulin G (IgG) complexes was carried out using sodium dodecyl sulfate--polyacrylamide gel electrophoresis (SDS-PAGE). Within ruminants, the following species showed two Tf molecules on SDS-PAGE; European and Zebu cattle, Bali cattle, banteng, two types of water buffalo, and two species of anoa. Other ruminants, sheep, goat, deer, antelope, camel, and giraffe, etc., showed only one Tf molecule. The Tf heterogeneity in molecular weight was, thus, restricted to Bos, Bubalus, and Anoa. The molecular weight of Tf of water buffalo was slightly larger than that of cattle on the gel. The peptide pattern from cyanogen bromide cleavage of Tf of the water buffalo differed clearly from that of cattle. Fetal Tf showed only one molecule during development, but a newborn calf has two Tf molecules, (one large and one small) within 18 hr after birth. We suggest, therefore, that the small molecules formed during the last month of gestation. The peptide patterns of adult and fetal Tfs cleaved by cyanogen bromide differed with regard to the two large peptides; fetal Tf, lacking the second-largest peptide, had twice the amount of the largest peptide compared with adult Tf. From these results, we suggest that a change in peptide sequence occurs from the last month of gestation, when the largest peptide is degraded to the second largest. However, a Tf-like protein detected in the liver microsomal fraction has only one molecular size, both in adult and in fetal livers.