Protonation-dependent stepped rotation of the F-type ATP synthase c-ring observed by single-molecule measurements
Year: 2017
Type: article
Abstract: The two opposed rotary molecular motors of the F 0 F 1 -ATP synthase work together to provide the majority of ATP in biological organisms. Rotation occurs in 120° power strokes separated by dwells when F 1 synthesizes or hydrolyzes ATP. F 0 and F 1 complexes connect via a central rotor stalk and a peripheral stator stalk. A major unresolved question is the mechanism in which the interaction between subunit-a and rotating subunit-c–ring in the F 0 motor uses the flux of H + across the membrane to induce clockwise rotation against the force of counterclockwise rotation driven by the F 1 -ATPase. In single-molecule measurements of F 0 F 1 embedded in lipid bilayer nanodiscs, we observed that the ability of the F 0 motor to form transient dwells increases with decreasing pH. Transient dwells can halt counterclockwise rotation powered by the F 1 -ATPase in steps equivalent to the rotation of single c-subunits in the c-ring of F 0 , and can push the common axle shared by the two motors clockwise by as much as one c-subunit. Because the F 0 proton half-channels that access the periplasm and the cytoplasm are exposed to the same pH, these data are consistent with the conclusion that the periplasmic half-channel is more easily protonated in a manner that halts ATPase-driven rotation by blocking ATPase-dependent proton pumping. The fit of transient dwell occurrence to the sum of three Gaussian curves suggests that the asymmetry of the three ATPase-dependent 120° power strokes imposed by the relative positions of the central and peripheral stalks affects c-subunit stepping efficiency.
Source: Journal of Biological Chemistry
Authors: Seiga Yanagisawa, Wayne D. Frasch
Institution: Arizona State University
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W2748970943