Interactions involved in grasping and locking of the inhibitory peptide IF1 by mitochondrial ATP synthase

When mitochondria become deenergized, futile ATP hydrolysis is prevented by reversible binding of an endogenous inhibitory peptide called IF1 to ATP synthase. Between initial IF1 binding and IF1 locking the enzyme experiences large conformational changes. While structural studies give access to analysis of the dead-end inhibited state, transient states have thus far not been described. Here, we studied both initial and final states by reporting, for the first time, the consequences of mutations of Saccharomyces cerevisiae ATP synthase on its inhibition by IF1. Kinetic studies allowed the identification of amino adds or motifs of the enzyme that are involved in recognition and/or locking of IF1 alpha-helical midpart. This led to an outline of IF1 binding process. In the recognition step, protruding parts of alpha and especially beta subunits grasp IF1, most likely by a few residues of its alpha-helical midpart. Locking IF1 within the alpha beta interface involves additional residues of both subunits. Interactions of the alpha and beta subunits with the foot of the gamma subunit might contribute to locking and stabilizing of the dead-end state. (C) 2014 Elsevier B.V. All rights reserved.