May catalyze the biosynthesis of cardiolipin from phosphatidylglycerol (PG) and CDP-diacylglycerol. 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycerol) + a CDP-1,2-diacyl-sn-glycerol = a cardiolipin + CMP + H(+) Lipid metabolism; phospholipid metabolism. Belongs to the CDP-alcohol phosphatidyltransferase class-I family.