F1-ATPase Is a Highly Efficient Molecular Motor that Rotates with Discrete 120° Steps

Abstract

A single molecule of F1-ATPase, a portion of ATP synthase, is by itself a rotary motor in which a central gamma subunit rotates against a surrounding cylinder made of alpha3beta3 subunits. Driven by three catalytic betas, each fueled with ATP, gamma makes discrete 120 degree steps, occasionally stepping backward. The work done in each step is constant over a broad range of imposed load and is close to the free energy of hydrolysis of one ATP molecule.

Operation mechanism of FoF1‐adenosine triphosphate synthase revealed by its structure and dynamics

“…F 1 waits for some elementary reaction steps during pauses, and generates torque during steps. The pauses and steps in rotation were first observed under substrate-limiting conditions (8). Under 1 lM ATP, F 1 showed distinct pauses at three angles, each 120 apart, waiting for ATP to bind (Fig.…”

“…To magnify the small turning radius (approximately, 1 nm) of the c-subunit, a large probe with the size of 0.1-0.5 lm is attached to the top of the c-subunit. A fluorescently labeled actin filament was used in early experiments (3,8). However, in recent studies, a plastic bead, magnetic bead, and colloidal gold are often used as the probe (Fig.…”

Bioenergetics and Biological Electron Transport

“…When 2 mM ATP was added to the solution, they observed the continuous rotation of the actin filament in an anti-clockwise direction when viewed from above (corresponding to the membrane side) with a rotational torque of $40 pN nm À1 . In subsequent experiments [125], they showed that at low ATP concentration, <mM, the g subunit rotates in a series of discrete 120 steps with an average mechanical work of 90 pN nm, corresponding to close to 100 % efficiency for ATP hydrolysis. Then, using high speed imaging [126], they were able to resolve the 120 rotation into 90 and 30 sub-steps, each lasting a fraction of a millisecond.…”

“…Evidence for this mechanism comes from a variety of sources, including radio labelling and specific cross-linking studies [119,120], fluorescent labelling studies [121], by nmr [122], by cross-linking [123] and through direct observation of single molecules using epi-fluorescent microscopy [124][125][126]. In these experiments, Yasuda et al immobilised F 1 -ATPase from E. coli onto Ni-NTA modified surfaces by histidine tagging of the a and b subunits.…”

Intragenic and intergenic suppression of the Escherichia coli ATP synthase subunit a mutation of Gly-213 to Asn: functional interactions between residues in the proton transport site

“…The catalytic domain, whose structure was solved by X-ray crystallography [5], consists of α $ β $ γ with one active site in each β subunit with some contribution from the neighbouring α subunit. Rotation of the γ subunit relative to the α $ β $ hexamer has been shown to have an integral role in steady-state turnover [6][7][8][9].…”