Rotational mechanism of Enterococcus hirae V1-ATPase by crystal-structure and single-molecule analyses

• Hybrid methods are a powerful approach to elucidate mechanisms of molecular machines.
• A rotary molecular motor was analyzed by structural and single-molecule methods.
• Asymmetric crystal structures of a bacterial V1-ATPase have been revealed.
• Rotary dynamics and torque generation of the same V1-ATPase have also been revealed.
• A chemo-mechanical coupling scheme based on results of this approach is proposed.

In ion-transporting rotary ATPases, the mechanical rotation of inner rotor subunits against other stator subunits in the complex mediates conversion of chemical free energy from ATP hydrolysis into electrochemical potential by pumping ions across the cell membrane. To fully understand the rotational mechanism of energy conversion, it is essential to analyze a target sample by multiple advanced methods that differ in spatiotemporal resolutions and sample environments. Here, we describe such a strategy applied to the water-soluble V1 moiety of Enterococcus hirae V-ATPase; this strategy involves integration of crystal structure studies and single-molecule analysis of rotary dynamics and torque generation. In addition, we describe our current model of the chemo-mechanical coupling scheme obtained by this approach, as well as future prospects.