Energy-driven subunit rotation at the interface between subunit a and the c oligomer in the FO sector of Escherichia coli ATP synthase
AUTOR(ES)
Hutcheon, Marcus L.
FONTE
The National Academy of Sciences
RESUMO
Subunit rotation within the F1 catalytic sector of the ATP synthase has been well documented, identifying the synthase as the smallest known rotary motor. In the membrane-embedded FO sector, it is thought that proton transport occurs at a rotor/stator interface between the oligomeric ring of c subunits (rotor) and the single-copy a subunit (stator). Here we report evidence for an energy-dependent rotation at this interface. FOF1 was expressed with a pair of substituted cysteines positioned to allow an intersubunit disulfide crosslink between subunit a and a c subunit [aN214C/cM65C; Jiang, W. & Fillingame, R. H. (1998) Proc. Natl. Acad. Sci. USA 95, 6607–6612]. Membranes were treated with N,N′-dicyclohexyl-[14C]carbodiimide to radiolabel the D61 residue on less than 20% of the c subunits. After oxidation to form an a–c crosslink, the c subunit properly aligned to crosslink to subunit a was found to contain very little 14C label relative to other members of the c ring. However, exposure to MgATP before oxidation significantly increased the radiolabel in the a–c crosslink, indicating that a different c subunit was now aligned with subunit a. This increase was not induced by exposure to MgADP/Pi. Furthermore, preincubation with MgADP and azide to inhibit F1 or with high concentrations of N,N′-dicyclohexylcarbodiimide to label most c subunits prevented the ATP effect. These results provide evidence for an energy-dependent rotation of the c ring relative to subunit a.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=37468Documentos Relacionados
- Rotation of the c subunit oligomer in fully functional F1Fo ATP synthase
- Subunit rotation in Escherichia coli FoF1–ATP synthase during oxidative phosphorylation
- ATP-driven stepwise rotation of FoF1-ATP synthase
- 36° step size of proton-driven c-ring rotation in FoF1-ATP synthase
- Subunit rotation of ATP synthase embedded in membranes: a or β subunit rotation relative to the c subunit ring