title: Function of the F1-motor (F1-ATPase) of ATP synthase by apolar-polar repulsion through internal interfacial water.
abstract: Within the structurally-confined internal aqueous cavity of the F1-motor of ATP synthase, function results from free energy changes that shift the balance between interfacial charge hydration and interfacial hydrophobic hydration. TRANSITION STATE DESCRIPTION: At the beta-P end of ADP x Mg occurs an inorganic phosphate, P(i). This P(i) resides at the base of a water-filled cleft that functions like an aperture to focus, into an aqueous chamber, a competition for hydration (an apolar-polar repulsion) between charged phosphate and hydrophobic surface of the gamma-rotor. Two means available for the phosphate and the hydrophobic surface to improve their hydration free energies are physically to separate by rotation of the gamma-rotor or chemically to combine P(i) with ADP to form less charged ATP. This proposal derives from calculated changes in Gibbs free energy for hydrophobic association of amino acid side chains and chemical modifications thereof and from experimentally demonstrated water-mediated repulsion between hydrophobic and charged sites that resulted from extensive studies on designed elastic-contractile model proteins.
authors.affiliation: BioTechnology Institute, University of Minnesota, Twin Cities Campus, 1479 Gortner Avenue, Suite 240, St. Paul, MN 55108-6106, USA. urryx001@tc.umn.edu
authors.forename: Dan W
authors.initials: DW
authors.lastname: Urry
mesh_terms: D020134:Catalytic Domain; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D025261:Mitochondrial Proton-Translocating ATPases / Q000737:chemistry*; D008958:Models, Molecular; D020409:Molecular Motor Proteins; D020836:Protein Structure, Quaternary; D006180:Proton-Translocating ATPases / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013499:Surface Properties; D019415:Torque; D014867:Water / Q000502:physiology*
chemical_list: D020409:Molecular Motor Proteins; D014867:Water; D025261:Mitochondrial Proton-Translocating ATPases; D006180:Proton-Translocating ATPases