Regulation of Proton Conduction

The most difficult and interesting question about H+-ATPase is how chemical reaction (ATP synthesis/ hydrolysis) is coupled with vectorial H+ conduction. The mechanism for the stoichiometric coupling between chemical reaction and vectorial transport of ions is a universal question for ion-motive ATPases. The Fo portion is a passive proton pathway but becomes a regulated pathway after the binding of Fi. Mutant analyses suggest that the y subunit has regulatory role(s) for proton conduction. 

Membrane vesicles (100 pg protein) from strain KFlOrA (yGln-14—.end) harboring mutant or wild-type plasmids were suspended in buffer containing 1 pM acridine orange, and fluorescence was monitored at 25° C. At the indicated times, 1 mM ATP or 1 pM CCCP was added. Membrane ATPase activities of mutants and wild type are also shown. 

We are grateful to Dr. T. Noumi for collaboration in the early part of the work discussed in this article. We thank Dr. Toshio Fukui for collaboration in affinity labeling of Fi with 

The most recent work from our laboratory was in collaboration with Dr. Robert K. Nakamoto, Dr. Hiroshi Omote, Dr. Yoshinori Moriyama, and students whose names appear in the references. Their contribution is greatly appreciated. 

Racker, A New Look at Mechanism in Bioenergetics, Academic Press, New York (1976). 

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