Active Ca2+ transport by vesicles reconstituted from Triton X-100-solubilized pigeon erythrocyte membrane

Pigeon erythrocyte membrane was solubilized partially, but relatively unselectively by Triton X-100. Vesicles were reconstituted from mixtures of Triton-solubilized membrane and lipid (phosphatidylcholine plus phosphatidyl-ethanolamine plus cholesterol) by addition of bovine high-density lipoprotein. This efficiently removed the Triton X-100. Sodium dodecyl sulfate-polyacrylamide gel electropherograms of reconstituted vesicles showed band patterns resembling those of the original membrane. The reconstituted vesicles showed ATP-dependent active accumulation of 45Ca2+. ATP-dependent 45Ca2+ uptake by the reconstituted vesicles resembled the corresponding activity of the original membrane vesicles; in both preparations the Ca2+ uptake rate depended on the square of the Ca2+ concentration and had similar [Ca2+]1/2 values, 0.16 microM and 0.18 microM, respectively.