The Complete Amino-Acid Sequence of Guinea-Pig alpha-Lactalbumin

Reduced, S-aminoethylated guinea-pig α-lactalbumin was cleaved with cyanogen bromide at its single methionyl residue. The products were separated gel by filtration and characterized by amino acid analysis and N-terminal group determination, as a 90-residue peptide from the N-terminus of the protein (N-terminal lysine) and a 33-residue peptide from the C-terminus of the protein (N-terminal aminoethyl cysteine). The amino acid sequences of both these peptides were determined by examination of the peptides obtained by digestion of the purified fragments with trypsin, chymotrypsin or thermolysin. The complete amino acid sequence of guinea-pig α-lactalbumin thus obtained is discussed in relation to the known sequences of other members of the lysozyme-α-lactalbumin group.