Golgi membranes of the yeast, Saccharomyces cerevisiae, were isolated by a method similar to the procedure described by Cleves et al. [Cell 64 (1991) 789–800]. Marker proteins of the Golgi, such as Kex2 protease and GDPase, are highly enriched in these preparations. The phospholipid and ergosterol content of Golgi membranes is low. Phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol are the major phospholipids of this compartment. The amount of phosphatidylserine in the Golgi is significantly higher than in yeast bulk membranes. Inositol-containing sphingolipids, especially inositolphosphorylceramide, are highly enriched in Golgi membranes. Two phospholipid-synthesizing enzymes, namely phosphatidylinositol synthase and sn-1,2-diacylglycerol cholinephosphotransferase, are detected in the Golgi at a specific activity which exceeds that of the endoplasmic reticulum.
