SUMMARY: Mutants of resistant to mevinolin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme-A (HMGCoA) reductase (EC were isolated and one mutant (MV71) was extensively characterized. While growth of resistant strains in the presence of mevinolin was greater than that of the wild-type strain, mevinolin at the concentration used still inhibited growth. Diploids produced by mutant/wild-type matings showed levels of mevinolin resistance which indicated incomplete dominance. Sterol synthesis in the presence of mevinolin was inhibited in strain MV71 but to a lesser degree than seen in the wild-type strain. All mevinolin resistant mutants also demonstrated a slight resistance to the antibiotic nystatin. The subcellular location of HMGCoA reductase activity in MV71 and the wild-type strain were determined and it was shown that yeast HMGCoA reductase is not regulated by a dephosphorylation mechanism as has been shown for mammalian reductases. and studies of strain MV71 and the wild-type indicated that mevinolin resistance did not result in changes in HMGCoA reductase activity as has been demonstrated in mammalian systems. Based on growth data, sterol analysis, and the lack of detection of HMGCoA reductase activity differences between strain MV71 and the wild-type, mevinolin resistance is concluded to result possibly from a mutation in , one of the two functional yeast HMGCoA reductase genes, which accounts for a minor (up to 17%) amount of total cellular reductase activity.


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