Abstract
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 ε engages the α, β and γ 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 ε 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 ε 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 ε C-terminal domain from entering the inhibitory 'up' state.
Highlights
The majority of metabolic energy in cells is generated by F1Fo ATP synthase, a biological rotary motor that converts the proton motive force to adenosine tri-phosphate (ATP) in both oxidative phosphorylation and photophosphorylation (Stewart et al, 2014; Walker, 2013)
The structural information obtained here using E. coli F1Fo ATP synthase incubated with MgATP likely reflects conformations uninhibited by the eCTD
Because the ATP and ADP concentrations present were comparable to those observed in intact cells (Bennett et al, 2009) it is likely that both these conformations are present in E. coli
Summary
The majority of metabolic energy in cells is generated by F1Fo ATP synthase, a biological rotary motor that converts the proton motive force (pmf) to adenosine tri-phosphate (ATP) in both oxidative phosphorylation and photophosphorylation (Stewart et al, 2014; Walker, 2013). The Fo motor spans the membrane and converts the potential energy of the pmf into rotation of the central stalk that in turn drives conformational changes in the three catalytic sites of the a3b3 F1 motor subunits to generate ATP This process is reversible so that, if the pmf drops below the threshold needed to power ATP synthesis, the motor has the ability to reverse and, in some bacterial species, operates primarily as a proton pump driven by ATP hydrolysis. Regulation of these ATPase/synthase activities is important in times of cellular stress, primarily to prevent wasteful ATP consumption. Different regulatory mechanisms are used by different F1Fo subtypes (bacterial, chloroplastic, mitochondrial) and species
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