Comparison of cytidinediphospho-sn-1,2-diglyceride transfer from microsomal and liposomal to mitochondrial membranes

Transfer of 3H]CDP-diglycerides from isolated guinea pig liver microsomal and liposomal membranes to guinea pig mitochondrial membranes was studied by incubating microsomal or liposomal membranes carrying 3H]CDP-diglycerides with mitochondrial membranes and determining the CDP-diglyceride-dependent incorporation of sn-3-14C]glycerolphosphate into mitochondrial 14C]polyglycerophosphatides. A significant difference in the amount of transferred 3H]CDP-diglycerides and the composition of mitochondrial 14C]polyglycerophosphatides was found depending on whether 3H]CDP-diglycerides were transferred from microsomal or liposomal membranes. This amount was around 12% when 3H]CDP-diglycerides were transferred from the microsomal membranes and around 4.6% when they were transferred from the liposomal membranes. Furthermore, about 60% of 14C]phosphatidylglycerol and 35% of 14C]phosphatidylglycerophosphate were found in the microsomes-mitochondria system and about 9% of 14C]phosphatidylglycerol and 79% of 14C]phosphatidylglycerophosphate were found in the liposomes-mitochondria system, establishing an important role for the membrane donor in the transfer of 3H]CDP-diglycerides to mitochondria. Furthermore, if the transfer of 3H]CDP-diglycerides from the microsomal to the mitochondrial membranes was assayed by the determination of 3H]CDP-diglycerides in reisolated mitochondrial membranes without further incorporation into mitochondrial polyglycerophosphates, it amounted to about 38%.