Purine, but not pyrimidine, nucleotides support rotation of F1-ATPase.

The binding change model for the

Molecular mechanism on forcible ejection of ATPase inhibitory factor 1 from mitochondrial ATP synthase

IF1 is a natural inhibitor of mitochondrial FoF1-ATP synthase, which blocks catalysis and rotation of the F1 motor. Here, the authors show the rotational-direction-dependence of activation from IF1 inhibition, with IF1 being readily dissociated when F1 rotates to the clockwise direction

Mechanically driven ATP synthesis by F-1-ATPase

ATP, the main biological energy currency, is synthesized from ADP and inorganic phosphate by ATP synthase in an energy-requiring reaction(1-3). The F-1 portion of ATP synthase, also known as F-1-ATPase, functions as a rotary molecular motor: in vitro its gamma-subunit rotates(4) against the surrounding alpha(3)beta(3) subunits(5), hydrolysing ATP in three separate catalytic sites on the beta-subunits. It is widely believed that reverse rotation of the gamma-subunit, driven by proton flow through the associated F-o portion of ATP synthase, leads to ATP synthesis in biological systems(1-3,6,7). Here we present direct evidence for the chemical synthesis of ATP driven by mechanical energy. We attached a magnetic bead to the gamma-subunit of isolated F-1 on a glass surface, and rotated the bead using electrical magnets. Rotation in the appropriate direction resulted in the appearance of ATP in the medium as detected by the luciferase-luciferin reaction. This shows that a vectorial force ( torque) working at one particular point on a protein machine can influence a chemical reaction occurring in physically remote catalytic sites, driving the reaction far from equilibrium

Torque Generation in F1-ATPase Devoid of the Entire Amino-Terminal Helix of the Rotor That Fills Half of the Stator Orifice

F1-ATPase is an ATP-driven rotary molecular motor in which the central γ-subunit rotates inside a cylinder made of α3β3 subunits. The amino and carboxyl termini of the γ rotor form a coiled coil of α-helices that penetrates the stator cylinder to serve as an axle. Crystal structures indicate that the axle is supported by the stator at two positions, at the orifice and by the hydrophobic sleeve surrounding the axle tip. The sleeve contacts are almost exclusively to the longer carboxyl-terminal helix, whereas nearly half the orifice contacts are to the amino-terminal helix. Here, we truncated the amino-terminal helix stepwise up to 50 residues, removing one half of the axle all the way up and far beyond the orifice. The half-sliced axle still rotated with an unloaded speed a quarter of the wild-type speed, with torque nearly half the wild-type torque. The truncations were made in a construct where the rotor tip was connected to a β-subunit via a short peptide linker. Linking alone did not change the rotational characteristics significantly. These and previous results show that nearly half the normal torque is generated if rotor-stator interactions either at the orifice or at the sleeve are preserved, suggesting that the make of the motor is quite robust