Comparison of bovine serum transferrin A and D2. I. Amino acid residue differences

Abstract

A comparison is made of single components of the homozygous variants A and D₂ of bovine serum transferrin by tryptic, chymotryptic and cyanogen bromide digestion. It is concluded that there are three substitutions A:D₂ ‐ Glu:Asp, Lys: Arg and Asp:Gly. In the light of the recent work of Brocket al. (1980) it is concluded that all three substitutions occur in the C‐terminal sequence of the chain. By homology with the sequence of human serum transferrin (MacGillivray et al., 1982) the Lys:Arg and Asp:Gly substitutions probably occur at residues 527 and 446, respectively, from the N‐terminus. The Asp:Gly substitution is considered more likely than our earlier conclusion (Maeda, McKenzie & Shaw, 1977) that there is a deletion in the chain of D₂ (A:D₂, Asp: —). The location of the Glu:Asp substitution is not known.