Growth of a sterol auxotroph derived fromSaccharomyces cerevisiae on chemically synthesized derivatives of cholesterol possessing side-chain modifications.

A number of cholesterol derivatives were analyzed for their ability to satisfy bulk membrane and high-specificity sparking requirements of a yeast sterol auxotroph (RD5-R) (Rodriguez, R. J., Taylor, F. R., and Parks, L. W. [1982], Biochem. Biophys. Res. Commun. 106, 435-441). Substitution of hydrogen by bromine or iodine at C-26 or substitution of C26-methyl by bromine enabled the resulting sterol to satisfy bulk or sparking functions. The presence of a side-chain hydroxyl or keto group at C-25 on a 26-norcholesterol completely abolished the ability of cholesterol to satisfy either sterol requirement. Growth studies revealed that, while the oxygenated cholesterol derivatives were not growth-supportive of RD5-R, they were not growth-inhibitory.