Figure 1: Coupling scheme for the 120° rotation and ATP hydrolysis of mammalian F1- and Enterococcus hirae V1-ATPases.
From: Crystal structures of the ATP-binding and ADP-release dwells of the V1 rotary motor
Each circle represents the chemical state of the nucleotide-binding site, viewed from the cytoplasmic side (that is, the N-terminal β-barrel side of V1). The central arrows in the ellipses represent the orientation of the central axis beginning from the twelve o’clock position, which corresponds to the ATP-binding dwell (a waiting state for ATP binding). PDB ID numbers of the corresponding crystal structures are shown under the schemes. ATP* represents an ATP molecule that is committed to hydrolysis. (a–d) A model for mammalian F1 (refs 22, 23). ATP binding to the ATP-binding dwell (a) induces a 65° rotation concomitant with ADP release from another binding site and resulting conformational changes to the Pi-release dwell7,9,23 (b). Pi release induces a 25° rotation and consequent conformational changes to the catalytic dwell11,23 (c), which is waiting for ATP hydrolysis. ATP* hydrolysis to produce ADP and Pi induces a 30° rotation and conformational changes to the ATP-binding dwell (d). (e–h) A model for E. hirae V1 (this study). ATP binding to the ATP-binding dwell (e) induces conformational changes to the ADP-release dwell (f) without an apparent rotational substep of the central axis. ADP release induces a 120° rotation and consequent conformational changes to the catalytic dwell (g). ATP* is hydrolysed to produce ADP and Pi, and the Pi release induces conformational changes to the ATP-binding dwell state (h) without a rotational substep.
