CDP-diacylglycerol--glycerol-3-phosphate 3-phosphatidyltransferase (EC:2.7.8.5), also known as phosphatidylglycerophosphate synthase, glycerophosphate phosphatidyltransferase and PGP synthase, catalyses the conversion ofCDP-diacylglycerol and glycerol-3-phosphate to CMP and 3-(3-phosphatidyl)-glycerol 1-phosphate in the commited step to the synthesis of acidic phospholipids. It is an integral membrane protein. A number of related enzymes are quite similar in both sequence and catalytic activity, including Saccharomyces cerevisiae (Baker's yeast) YDL142c, now known to be a cardiolipin synthase. There may be problems with incorrect transitive annotation of near homologs as authentic CDP-diacylglycerol--glycerol-3-phosphate 3-phosphatidyltransferase.