| The mixed function oxidase system is an endoplasmic reticulum-bound multienzyme electron transport system that provides the oxidative steps in the distribution of the atoms of oxygen to yield water and oxidized substrate. In the yeast Candida tropicalis, the flavoprotein NADPH-cytochrome P450 oxidoreductase (E.C.1.6.2.4), (CPR), provides electrons to two terminal oxidases: {dollar}sp{lcub}rm P450{rcub}{dollar}14DM (lanosterol 14{dollar}alpha{dollar}-demethylase) and P450alk ({dollar}eta{dollar}-alkane {dollar}omega{dollar}-hydroxylase). Here I report the isolation and sequence characterization of the Candida tropicalis CPR gene, its induction by growth on n-alkane and its expression in Saccharomyces cerevisiae. Comparison of the deduced CPR amino acid sequence with mammalian CPR sequences reveals extensive homologies that indicate this enzyme is conserved in structure and function. In addition the Candida tropicalis CPR gene has been used to isolate its orthologue, CPR1, from Saccharomyces cerevisiae. Gene replacement experiments in this yeast address the essentiality of CPR1 in yeast and its function as a major component of the mixed function oxidase system. Growth inhibition studies using ketoconazole in CPR1 null mutants suggest that this protein will provide a new site of action for antifungal drugs. |
