Cryo-EM reveals distinct conformations of E-coli ATP synthase on exposure to ATP

ATP synthase produces the majority of cellular energy in most cells. We have previously reported cryo-EM maps of autoinhibited E. coli ATP synthase imaged without addition of nucleotide (Sobti et al. 2016), indicating that the subunit epsilon engages the alpha, beta and gamma subunits to lock the enzyme and prevent functional rotation. Here we present multiple cryo-EM reconstructions of the enzyme frozen after the addition of MgATP to identify the changes that occur when this epsilon inhibition is removed. The maps generated show that, after exposure to MgATP, E. coli ATP synthase adopts a different conformation with a catalytic subunit changing conformation substantially and the epsilon C-terminal domain transitioning via an intermediate 'half-up' state to a condensed 'down' state. This work provides direct evidence for unique conformational states that occur in E. coli ATP synthase when ATP binding prevents the epsilon C-terminal domain from entering the inhibitory 'up' state.