This protein catalyzes the committed step to the synthesis of the acidic phospholipids. a CDP-1,2-diacyl-sn-glycerol + sn-glycerol 3-phosphate = 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycero-3'-phosphate) + CMP + H(+) Phospholipid metabolism; phosphatidylglycerol biosynthesis; phosphatidylglycerol from CDP-diacylglycerol: step 1/2. The N-terminus is probably blocked. Belongs to the CDP-alcohol phosphatidyltransferase class-I family.