Download MendeleyMicroscopic Rotary Mechanism of Ion Translocation in the Fo Complex of ATP Synthases
Pogoryelov, D., Krah, A., Langer, J., Yildiz, O., Faraldo-Gomez, J.D., Meier, T.(2010) Nat Chem Biol 6: 891
- PubMed: 20972431
- DOI: https://doi.org/10.1038/nchembio.457
- Primary Citation of Related Structures:
2XQS, 2XQT, 2XQU - PubMed 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.
Organizational Affiliation:
Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
