Engineering Approaches to Biomolecular Motors

Engineering Approaches to Biomolecular Motors: From in vitro to in vivo Thursday Speaker Abstracts

Robustness of Allostery and Torque-transmission of F1-ATPase Learned from Engineering Approach Hiroyuki Noji . University of Tokyo, Japan. F1-ATPase is a rotary motor protein in which the inner subunit rotates against the surrounding stator ring upon ATP hydrolysis. The stator ring is composed of 3 alpha and 3 beta subunits, and the catalytic reaction centers are located on the 3 alpha-beta interfaces, mainly on the beta subunits. The unique feature of F1-ATPase that discriminates F1-ATPase 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. 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 beta subunits with the rotary shaft subunit. However, recent experiments showed the rotation mechanism is far more robust than we thought before; even after removing the rotary shaft, the remaining stator ring undergoes cooperative power stroke motion among 3 beta subunits (Uchihashi et al. Science 2013). 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 (Iwamoto et al. unpublished data).

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