A Partial Amino Acid Sequence of α-Lactalbumin-I of the Grey Kangaroo (Macropus giganteus)

Two types of cu-l&albumin were separated chromatographically from the milk of the grey kangaroo and were found to have very similar amino acid compositions.Analysis of one type resulted in elucidation of the sequence of 42 residues from the NH2 terminus of the molecule.Only 7 of the first 22 residues in the kangaroo molecule were identical with corresponding residues in either of three cr-lactalbumins from other mammalian species.The sequence from residues 23 to 42 in the kangaroo protein is very similar to the other a-lactalbumin sequences.There is also considerable sequence similarity between kangaroo ol-lactalbumin and human and chicken lysozymes.Other structural features, however, appear to be unique to kangaroo cY-lactalbumin.Comparison of the sequences of the cY-lactalbumins from the kangaroo, man, cow, and guinea pig with those of human and chicken lysozyme give additional insight into the evolutionary relationships of these proteins as well as the structural basis of oc-lactalbumin function.