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Nat Struct Mol Biol. 2009 Oct;16(10):1068-73. doi: 10.1038/nsmb.1678. Epub 2009 Sep 27.

High-resolution structure of the rotor ring of a proton-dependent ATP synthase.

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1
Department of Structural Biology, Max-Planck Institute of Biophysics, Frankfurt am Main, Germany.

Abstract

The crystal structure of the c-ring from the proton-coupled F1Fo ATP synthase from Spirulina platensis is shown at 2.1-A resolution. The ring includes 15 membrane-embedded c subunits forming an hourglass-shaped assembly. The structure demonstrates that proton translocation across the membrane entails protonation of a conserved glutamate located near the membrane center in the c subunit outer helix. The proton is locked in this site by a precise hydrogen bond network reminiscent of that in Na+-dependent ATP synthases. However, the structure suggests that the different coordination chemistry of the bound proton and the smaller curvature of the outer helix drastically enhance the selectivity of the H+ site against other cations, including H3O+. We propose a model for proton translocation whereby the c subunits remain in this proton-locked state when facing the membrane lipid. Proton exchange would occur in a more hydrophilic and electrostatically distinct environment upon contact with the a subunit interface.

PMID:
19783985
DOI:
10.1038/nsmb.1678
[Indexed for MEDLINE]
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