Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
Daniel G Schep
The Hospital for Sick Children Research Institute, Toronto, Canada; Department of Medical Biophysics, The University of Toronto, Ontario, Canada
John V Bason
MRC Mitochondrial Biology Unit, Cambridge, United Kingdom
Martin G Montgomery
MRC Mitochondrial Biology Unit, Cambridge, United Kingdom
John E Walker
MRC Mitochondrial Biology Unit, Cambridge, United Kingdom
Nikolaus Grigorieff
Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
John L Rubinstein
The Hospital for Sick Children Research Institute, Toronto, Canada; Department of Medical Biophysics, The University of Toronto, Ontario, Canada; Department of Biochemistry, The University of Toronto, Ontario, Canada
Adenosine triphosphate (ATP), the chemical energy currency of biology, is synthesized in eukaryotic cells primarily by the mitochondrial ATP synthase. ATP synthases operate by a rotary catalytic mechanism where proton translocation through the membrane-inserted FO region is coupled to ATP synthesis in the catalytic F1 region via rotation of a central rotor subcomplex. We report here single particle electron cryomicroscopy (cryo-EM) analysis of the bovine mitochondrial ATP synthase. Combining cryo-EM data with bioinformatic analysis allowed us to determine the fold of the a subunit, suggesting a proton translocation path through the FO region that involves both the a and b subunits. 3D classification of images revealed seven distinct states of the enzyme that show different modes of bending and twisting in the intact ATP synthase. Rotational fluctuations of the c8-ring within the FO region support a Brownian ratchet mechanism for proton-translocation-driven rotation in ATP synthases.
