Isolation, purification, amino acid sequence determination and X-ray crystal structure of buffalo α-lactalbumin were performed in order to gain further knowledge of the molecular basis of α-lactalbumin in the lactose synthase complex. The deduced amino acid sequence differs at one position from the bovine α-lactalbumin sequence (at position 17). The refined crystal structure at 2.3 Å is very similar to those previously reported for human and baboon α-lactalbumins. However, a portion of the molecule (residues 105–109) exhibits different conformation. It forms a ‘flexible loop’, and appears to be a functionally important region in forming the lactose synthase complex.
