Mechanical inhibition of isolated V_o from V/A-ATPase for proton conductance.

Abstract

V-ATPase is an energy converting enzyme, coupling ATP hydrolysis/synthesis in the hydrophilic V₁ domain, with proton flow through the V_o membrane domain, via rotation of the central rotor complex relative to the surrounding stator apparatus. Upon dissociation from the V₁ domain, the V_o domain of the eukaryotic V-ATPase can adopt a physiologically relevant auto-inhibited form in which proton conductance through the V_o domain is prevented, however the molecular mechanism of this inhibition is not fully understood. Using cryo-electron microscopy, we determined the structure of both the <i>holo</i> V/A-ATPase and isolated V_o at near-atomic resolution, respectively. These structures clarify how the isolated V_o domain adopts the auto-inhibited form and how the <i>holo</i> complex prevents formation of the inhibited V_o form.