Figure 2.

Deletion of GEM1 does not alter cellular and mitochondrial phospholipid profiles, or the transport dependent conversion of PS to PE. A) Transport of PS and conversion into PE was assayed in vivo by growing the indicated strains in medium containing [³H]-serine and analyzing the distribution of radioactivity among phospholipid classes. (B) Synthesis and transport of PS and conversion into PE was measured in vitro by pulse labeling the crude mitochondrial fraction with [³H]-serine for 15 minutes to radiolabel the PS pool, and then arresting further PS synthesis and following the conversion to [³H]-PE. The reactions were terminated by lipid extraction and the distribution of radioactivity among phospholipid classes was quantified. To assess steady state lipid content, lipids were also extracted from whole cells (C), or mitochondria isolated from psd2Δ and gem1Δ psd2Δ strains (D). Individual lipid classes were separated by two-dimensional TLC and quantified by measuring phosphorus. Bars and error bars represent the average and SD from three independent experiments. CL, cardiolipin; PA, phosphatidic acid. Other lipid abbreviations as in Figure 1.