Energy-linked activities in reconstituted yeast adenosine triphosphatase proteoliposome. Adenosine triphosphate formation coupled with electron flow between ascorbate and ferricyanide. |
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Authors: | I J Ryrie P F Blackmore |
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Institution: | Department of Developmental Biology, Research School of Biological Sciences, Australian National University, Canberra, A.C.T. 2601, Australia |
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Abstract: | (1) Conditions are described wherein the yeast oligomycin-sensitive adenosine triphosphatase (ATPase) complex can be reconstituted together with phospholipids to yield extremely high rates of ATP-32Pj exchange. The vesicles so formed exhibit proton uptake upon addition of Mg2+-ATP and a relatively slow decay of the proton gradient. (2) The stimulation of ATP-32Pi exchange by valinomycin + K+ reported previously (Ryrie, I. J. (1975) Arch. Biochem. Biophys. 168, 704–711) is apparently not simply due to a diffusion potential. The findings suggest that an electroimpelled, valinomycin-dependent migration of K+ may occur together with the electrogenic movements of protons during ATP hydrolysis and synthesis to establish optimal energized conditions for ATP-32Pi exchange. (3) An artificial oxidative phosphorylation system in the reconstituted vesicles is described: 32P]ATP formation from ADP and 32Pi is shown to be linked with electron flow between external ascorbate and internal ferricyanide where a permeable proton carrier, such as phenazine methosulfate, is used to establish a proton gradient. That the yeast ATPase is capable of net ATP synthesis has also been demonstrated in a light-dependent reaction using ATPase proteoliposomes reconstituted together with bacteriorhodopsin. |
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