The control of Gene Expression by Membrane Organization in Saccharomyces Cerevisiae

Abstract

The facultative anaerobe, Saccharomyces cerevisiae, has considerable advantage as an organism for the study of mitochondrial membranes, as many parameters of mitochondrial membrane composition in this organism are subject to both physiological and genetic manipulation (for review see Linnane and Haslam, 1971). In particular, situations that result in the formation of defective organelles can be experimentally exploited, as the organism does not need respiratory metabolism for growth on fermentable substrates; thus cells of S.cerevisiae grown anaerobically on glucose or galactose media contain mitochondrial precursor structures that lack respiratory chain cytochromes and the capacity for oxidative phosphorylation. The ability of S. cerevisiae to grow anaerobically also allows the manipulation of the lipid composition of the mitochondrial membranes, since the organism is unable to synthesize unsaturated fatty acids (UFA) or ergosterol in the absence of molecular oxygen (Andreason and Stier, 1953; Bloomfield and Bloch, 1960), but can incorporate into its membranes a wide range of added sterols and UFA’s (Bloch et al., 1961; Proudlock et al., 1968). If lipids are present in the anaerobic growth medium in trace amounts, the growth of cells is limited and membrane lipid levels of both UFA and ergosterol fall to as low as one tenth of the values found in the presence of excess lipid supplements (Jollow et al., 1968; Watson et al., 1970; Watson et al., 1971). Recent investigations have shown that the nature of the anaerobic mitochondrial precursor structures is markedly dependent on lipid composition (Watson et al., 1970; Watson et al., 1971).