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Microscopic rotary mechanism of ion translocation in the Fo complex of ATP synthases

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Pogoryelov,  Denys
Department of Structural Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Krah,  Alexander
Max Planck Research Group of Theoretical Molecular Biophysics, Max Planck Institute of Biophysics, Max Planck Society;

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Langer,  Julian David
Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Yildiz,  Özkan
Department of Structural Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Faraldo-Gómez,  José D.
Max Planck Research Group of Theoretical Molecular Biophysics, Max Planck Institute of Biophysics, Max Planck Society;

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Meier,  Thomas
Department of Structural Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Citation

Pogoryelov, D., Krah, A., Langer, J. D., Yildiz, Ö., Faraldo-Gómez, J. D., & Meier, T. (2010). Microscopic rotary mechanism of ion translocation in the Fo complex of ATP synthases. Nature Chemical Biology, 6, 891-899. doi:10.1038/nchembio.457.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0024-D6F6-5
Abstract
The microscopic mechanism of coupled c-ring rotation and ion translocation in F(1)F(o)-ATP synthases is unknown. Here we present conclusive evidence supporting the notion that the ability of c-rings to rotate within the F(o) complex derives from the interplay between the ion-binding sites and their nonhomogenous microenvironment. This evidence rests on three atomic structures of the c(15) rotor from crystals grown at low pH, soaked at high pH and, after N,N'-dicyclohexylcarbodiimide (DCCD) modification, resolved at 1.8, 3.0 and 2.2 Å, respectively. Alongside a quantitative DCCD-labeling assay and free-energy molecular dynamics calculations, these data demonstrate how the thermodynamic stability of the so-called proton-locked state is maximized by the lipid membrane. By contrast, a hydrophilic environment at the a-subunit-c-ring interface appears to unlock the binding-site conformation and promotes proton exchange with the surrounding solution. Rotation thus occurs as c-subunits stochastically alternate between these environments, directionally biased by the electrochemical transmembrane gradient.