Inorganic pyrophosphate-driven ATP-synthesis in liposomes containing membrane-bound inorganic pyrophosphatase and F0-F1 complex from Rhodospirillum rubrum

AbstractPP1 driven ATP synthesis has been reconstituted in a liposomal system containing the membrane-bound energy-linked PP1ase and coupling factor complex, both highly purified from Rhodospirillum rubrum. This energy converting model system was made by mixing both enzyme preparations with an aqueous suspension of sonicated soybean phospholipids and subjecting to a freeze—thaw procedure. In the presence of ADP, Mg2+, P1 and PP1 the system catalyzed phosphorylation by up to 25 nmol ATP formed X mg protein−1 X min−1, at 20°C, which was sensitive to uncouplers and inhibitors of phosphorylation such as oligomycin, efrapeptin and N,N′-dicyclohexylcarbodiimide

Kinetics of the H+-ATPase in chromatophores from Rhodospirillum rubrum Effect of the electrical transmembrane potential on the rate constants

AbstractThe effect of the electrical potential on the H+-ATPase of Rhodospirillum rubrum is examined. It is shown that the forward reaction rate (ATP synthesis) is increased by a factor of 10 during illumination while the reversed rate is only slightly decreased. This indicates that the electrical potential across the membrane affects the rate constants mainly by increasing the forward rate constants rather than decreasing the reversed rate constants in order to go from net hydrolysis to net synthesis