STEROL SPECIFICITY OF THE SACCHAROMYCES-CEREVISIAE ERG6 GENE-PRODUCT EXPRESSED IN ESCHERICHIA-COLI

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