ATP-synthesis by proteoliposomes incorporating Rhodospirillum rubrum F0F1 as measured with firefly luciferase: dependence on delta psi and delta pH.
ATP-synthesis catalyzed by proteoliposomes incorporating Rhodospirillum rubrum F0F1 was driven by artificially applied electrochemical proton gradients. The time-course of ATP-synthesis was followed continuously by means of firefly luciferase. Correction methods were developed which allow one to calculate the initial rate of ATP-synthesis from the observed luminescence kinetics. The following results were obtained: (1) ATP-synthesis occurred above a threshold delta mu H+ of 90 mV; this threshold is not imposed by the activation requirement of the enzyme; (2) delta psi and delta pH appear to be equivalent as driving forces for ATP-synthesis if allowance is made for the effect of the electrical capacitance of the liposome membrane on the distribution of K+ at equilibrium; and (3) the highest rate observed so far is 200 mol ATP per mol F0F1 per s.
Slooten
L
L
Vrije Universiteit Brussel, Faculty of Sciences, Laboratory of Biophysics, Belgium.
Vandenbranden
S
S
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D001517:Coleoptera / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008081:Liposomes; D008156:Luciferases; D008433:Mathematics; D008962:Models, Theoretical; D011510:Proteolipids / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D012247:Rhodospirillum rubrum / Q000201:enzymology*
D008081:Liposomes; D011510:Proteolipids; C020485:proteoliposomes; D000255:Adenosine Triphosphate; D008156:Luciferases; D006180:Proton-Translocating ATPases