VTLSS Seminar: Robustness of rotary catalysis of F1-ATPase
Biocomplexity Institute of Virginia Tech, Conference Center (145)
Professor of Applied Chemistry, University of Tokyo
Abstract: F1-ATPase is a rotary motor protein in which the inner subunit rotates against the surrounding stator ring upon ATP hydrolysis(1,2). The stator ring is composed of 3 a and 3 b subunits, and the catalytic reaction centers are located on the 3 a-b interfaces, mainly on the b subunits.
The unique feature of F1-ATPase that discriminates it from other molecular motors is the high energy conversion efficiency and the reversibility of the chemomechanical coupling; when the rotation is forcibly reversed, F1-ATPase catalyzes ATP synthesis reaction against large free energy of ATP hydrolysis(3). The experimental verification that the rotary angle of the rotary shaft controls the chemical equilibrium of ATP hydrolysis/synthesis was thought to suggest that the 3 reaction centers communicate via the atomically fine-tuned molecular interaction of the b subunits with the rotary shaft subunit.
However, recent experiments showed the rotation mechanism is far more robust than we though before; even after removing the rotary shaft, the remaining stator ring undergoes cooperative power stroke motion among 3 b subunits(4).
This finding suggests that the allostery is programmed in the stator ring, pointing the possibility that an artificial rod-shaped molecule would be rotated in the stator ring of F1-ATPase. We tested this hypothesis by incorporating a xenogeneic protein in the stator ring. The artificial molecule showed unidirectional rotation although the generated torque is evidently lower than the wild-type F1-ATPase(5).