Sterol specificity of the Saccharomyces cerevisiae ERG6 gene product expressed in Escherichia coli

The ERG6 gene from Saccharomyces cerevisiae has been functionally expressed in Escherichia coli, for the first time, yielding a protein that catalyzes the bisubstrate transfer reaction whereby the reactive methyl group from (S)-adenosyl-L-methionine is transferred stereoselectively to C-24 of the sterol side chain. The structural requirements of sterol in binding and catalysis were similar to the native protein from S. cerevisiae. Inhibition of biomethylation was observed with fecosterol and ergosterol which suggests that ergosterol may function in wild-type yeast as a feedback regulator of sterol biosynthesis.