An electrophoretic examination is made of milk samples taken from eight Bali (banteng) cattle, Bos (Bibos) javanicus, at Beatrice Hills, Northern Territory, Australia. Starch-gel electrophoresis at pH 8· 5 (NaOH-H3B03 buffer) and filter-paper electrophoresis at pH 8· 6 (diethylbarbiturate buffer) indicate that all samples contain a new a-lactalbumin variant, designated a-lactalbumin C. The order of mobility for bovine variants is A > B > C. The C variant differs from the common B variant in having one more amide residue (substitution of Asn for Asp or GIn for Glu).Examination of milk samples by urea-starch-gel electrophoresis at alkaline pH indicates that there is a new asrcasein variant, designated as1-casein EBol;, present in some samples. No new K-casein variant is detected by this method (all samples typing as K-casein B). A new variant of jJ-casein, designated A4, is detected by urea-starch-gel electrophoresis at low pH.The variants of milk proteins observed in this paper and in Bell et al. (1981) are discussed in relation to those of other members of the Bovinae, especially the yak, Bos (Poephagus) grunniens.

An electrophoretic examination is made of samples of milk from eight Bali (banteng) cattle, Bos (Bibos) javanicus, in the Northern Territory of Australia. There are two new electrophoretically distinct bovine ft-Iactoglobulins, designated E and F, present in these samples. It is shown by amino acid analysis and tryptic peptide mapping of isolated samples that: (I) both E and F differ from the B variant of domestic cattle (Bos taurus) by + 1 G1y, -1 Glu at residue 157 or 158; and (2) the F variant has the additional charge differences from E and B due to + I Tyr, -1 Asp at residue 129 or 130. It is also shown by studies of peptides produced by the action of Staphylococcus aureus strain V8 protease and by more recent amino acid analyses that (1) the GlyjGlu substitution is at residue 158; (2) there is an additional Bali variant, designated ft-lactoglobulin G, differing from E by + 1 Met, -1 lie at residue 78, but having the same mobility as E; and (3) there is an hitherto undetected neutral residue substitution of + 1 Ser, -1 Pro at position 50 in the F variant. The relation of these variants to other known ft-lactoglobulin variants of the Bos genus is discussed.

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SummaryA 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.

SummaryGlycopeptides are isolated from subtilisin and pronase digests of whole bovine serum transferrin A and D2. The two variants yield glycopeptides with identical ami‐no acid composition. Hence, there is probably no amino acid substitution in this region of the peptide chain. Amino acid sequence determination of one glycopeptide (subtilisin glycopeptide 8) gives the sequence: (CHO)Asn‐Ser‐Ser‐Leu‐Cys. This sequence is identical with that of residues 491–495 of the sequence for human serum transferrin (MacGillivray et al., 1982) except that in the bovine transferrin, Asp is replaced by Asn, enabling carbohydrate attachment. A second glycopeptide sequence Arg‐(CHO)Asn‐Ala‐Thr‐Tyr is observed, and the significance discussed in relation to carbohydrate moieties of serum glycoproteins.