PROBING THE METAL BINDING SITES OF α-LACTALBUMIN WITH LASER-EXCITED Eu(III) IONS

α-lactalbumin, also known as the B-protein of the lactose synthetase enzymatic complex, is a soluble milk protein which is secreted throughout lactation and functions as an "on-off" switch in the synthesis of lactose. The protein has a molecular weight of 14,200 and contains 123 amino acid residues arranged in a sequence similar to that of egg-white lysozyme [1]. The protein in its native form contains one or two Ca(II) ions per mole but despite extensive investigation, mainly by Kronman and coworkers [2,3,4,8], the number and location of the sites for attachment of calcium remain ill-defined. We have initiated a study to determine further the number and nature of the protein metallic sites using Eu(III) as a luminescent binding probe