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Microscopic rotary mechanism of ion translocation in the F(o) complex of ATP synthases.

Nature chemical biology (2010-10-26)
Denys Pogoryelov, Alexander Krah, Julian D Langer, Özkan Yildiz, José D Faraldo-Gómez, Thomas Meier
摘要

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.

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Sigma-Aldrich
N,N′-二环己基碳二亚胺, 99%
Sigma-Aldrich
N,N′-二环己基碳二亚胺, puriss., ≥99.0% (GC)
Sigma-Aldrich
N,N′-二环己基碳二亚胺 溶液, 1.0 M in methylene chloride