Efficient expression of bovine alpha-lactalbumin in Saccharomyces cerevisiae

A synthetic gene encoding the mature bovine alpha-lactalbumin fused to the preproregion of the yeast alpha-mating factor has been expressed and secreted at high level in Saccharomyces cerevisiae under the control of the alpha-mating promoter. Growth conditions were found to be critical for the expression: recombinant alpha-lactalbumin could only be detected in the medium provided the culture was grown at neutral pH. The secreted bovine alpha-lactalbumin is enzymatically active and identical to the whey protein, as confirmed by SDS/PAGE, IEF, ultraviolet and CD spectral analysis, and amino-terminal sequence determination.