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Publication Abstract from PubMed

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 A, 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.

Microscopic rotary mechanism of ion translocation in the F(o) complex of ATP synthases.,Pogoryelov D, Krah A, Langer JD, Yildiz O, Faraldo-Gomez JD, Meier T Nat Chem Biol. 2010 Dec;6(12):891-9. Epub 2010 Oct 24. PMID:20972431^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.