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Engineering Approaches to Biomolecular Motors: From in vitro to in vivo Thursday Speaker Abstracts
17
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unpublished data).