LAUSR

Significance The reduction of molecules at negative reduction potentials is a necessity and a challenge in biology and chemistry. The electrons required for the reduction may be energized by coupling the reaction(s) to an exergonic process such as the fission of reactive bonds in compounds like ATP. Our study of different complexes between an ATP-hydrolyzing reductase and its associated negative reduction–potential electron acceptor reveal very similar spatial arrangements of functional elements within unrelated proteins, pointing to a convergent evolution of catalytic strategies. Their architectures allow conformational changes at the ATP-binding/hydrolysis site to be propagated within the complex.