Changes within the central stalk of E. coli F1Fo ATP synthase observed after addition of ATP

Abstract

F₁F_o ATP synthase functions as a biological generator and makes a major contribution to cellular energy production. Proton flow generates rotation in the F_o motor that is transferred to the F₁ motor to catalyze ATP production, with flexible F₁/F_o coupling required for efficient catalysis. F₁F_o ATP synthase can also operate in reverse, hydrolyzing ATP and pumping protons, and in bacteria this function can be regulated by an inhibitory ε subunit. Here we present cryo-EM data showing E. coli F₁F_o ATP synthase in different rotational and inhibited sub-states, observed following incubation with 10 mM MgATP. Our structures demonstrate how structural transitions within the inhibitory ε subunit induce torsional movement in the central stalk, thereby enabling its rotation within the F_ο motor. This highlights the importance of the central rotor for flexible coupling of the F₁ and F_o motors and provides further insight into the regulatory mechanism mediated by subunit ε.