High-resolution structure of the rotor ring of a proton-dependent ATP synthase.
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.
Pogoryelov
Denys
D
Department of Structural Biology, Max-Planck Institute of Biophysics, Frankfurt am Main, Germany.
Yildiz
Ozkan
O
Faraldo-Gómez
José D
JD
Meier
Thomas
T
D000595:Amino Acid Sequence; D025243:Bacterial Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics*; D001665:Binding Sites; D001692:Biological Transport; D002412:Cations; D007477:Ions; D008055:Lipids / Q000737:chemistry; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011522:Protons; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000737:chemistry; D053545:Spirulina / Q000201:enzymology* / Q000235:genetics; D055672:Static Electricity
D002412:Cations; D007477:Ions; D008055:Lipids; D011522:Protons; D012964:Sodium; D025243:Bacterial Proton-Translocating ATPases