α-Lactalbumin from bovine milk

α-Lactalbumin is a small, globular, whey protein that has been found in all milk studied to date. It is a metalloprotein of approximately 14 kDa produced in the mammary glands.

α-Lactalbumin from bovine milk has been used as a supplement of basal medium for various cell cultures. It has also been used as a marker for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

α-Lactalbumin is the cheif protein in human milk. It consists of a single polypeptide chain with 8 cysteines which form disulfide bridges. α-Lactalbumin binds several metal ions, including calcium, which is thought to play a role in the regeneration of native α-lactalbumin from the reduced, denatured form. α-Lactalbumin also has a distinct zinc binding site that is thought to play a role in the binding of the lactose synthase complex. The mature protein consists of 123 amino acid residues (14 kD), and it has a three-dimensional structure with 1.7 Α° resolution, demonstrating four α-helices and a triple stranded antiparallel β-sheet.

Alters the substrate specificity of galactosyltransferase to increase the rate of lactose formation; the complex of galactosyltransferase and α-lactalbumin is called lactose synthase.

Alters the substrate specificity of galactosyltransferase to increase the rate of lactose formation; the complex of galactosyltransferase and α-lactalbumin is called lactose synthase. Site-directed mutagenesis of Asp⁸⁷ or Asp⁸⁸ to Ala completely abolishes the strong calcium binding affinity and reduces the stimulation of lactose synthase to <3.5% of the maximal rate.

Calcium saturated. May have traces of ammonium sulfate and sodium phosphate