title: Electric field driven torque in ATP synthase.
abstract: FO-ATP synthase (FO) is a rotary motor that converts potential energy from ions, usually protons, moving from high- to low-potential sides of a membrane into torque and rotary motion. Here we propose a mechanism whereby electric fields emanating from the proton entry and exit channels act on asymmetric charge distributions in the c-ring, due to protonated and deprotonated sites, and drive it to rotate. The model predicts a scaling between time-averaged torque and proton motive force, which can be hindered by mutations that adversely affect the channels. The torque created by the c-ring of FO drives the γ-subunit to rotate within the ATP-producing complex (F1) overcoming, with the aid of thermal fluctuations, an opposing torque that rises and falls with angular position. Using the analogy with thermal Brownian motion of a particle in a tilted washboard potential, we compute ATP production rates vs. proton motive force. The latter shows a minimum, needed to drive ATP production, which scales inversely with the number of proton binding sites on the c-ring.
authors.affiliation: Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, Texas, United States of America.
authors.forename: John H
authors.initials: JH
authors.lastname: Miller
authors.forename: Kimal I
authors.initials: KI
authors.lastname: Rajapakshe
authors.forename: Hans L
authors.initials: HL
authors.lastname: Infante
authors.forename: James R
authors.initials: JR
authors.lastname: Claycomb
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D001665:Binding Sites; D055592:Biophysical Phenomena; D002462:Cell Membrane / Q000378:metabolism; D004563:Electrochemistry; D004926:Escherichia coli / Q000201:enzymology*; D006112:Gravitation; D006358:Hot Temperature; D006801:Humans; D008928:Mitochondria / Q000201:enzymology; D008962:Models, Theoretical; D020409:Molecular Motor Proteins / Q000378:metabolism; D018892:Proton-Motive Force; D006180:Proton-Translocating ATPases / Q000737:chemistry*; D017382:Reactive Oxygen Species; D019415:Torque
chemical_list: D020409:Molecular Motor Proteins; D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases
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