* To whom correspondence should be addressed.
Received April 18, 2012; Revision received June 1, 2012
Changes in respiratory activity, transmembrane electric potential, and ATP synthesis as induced by additions of limited amounts of ADP and Pi to tightly coupled inverted (inside-out) Paracoccus denitrificans plasma membrane vesicles were traced. The pattern of the changes was qualitatively the same as those observed for coupled mitochondria during the classical State 4–State 3–State 4 transition. Bacterial vesicles devoid of energy-dependent permeability barriers for the substrates of oxidation and phosphorylation were used as a simple experimental model to investigate two possible mechanisms of respiratory control: (i) in State 4 phosphoryl transfer potential (ATP/ADP × Pi) is equilibrated with proton-motive force by reversibly operating F1·Fo-ATPase (thermodynamic control); (ii) in State 4 apparent “equilibrium” is reached by unidirectional operation of proton motive force-activated F1·Fo-ATP synthase. The data support the kinetic mechanism of the respiratory control phenomenon.
KEY WORDS: FoF1-H+-ATP synthase, oxidative phosphorylation, bacterial plasma membrane, Paracoccus denitrificans