The detailed molecular mechanism of ATP synthesis in the F0 portion of ATP synthase reveals a non-chemiosmotic mode of energy coupling

Abstract

Based on our torsional mechanism of ion translocation, energy transduction and energy storage in ATP synthase [Curr. Sci. 75(1998) 716]; [Curr. Sci. 77 (1999) 167]; [Curr. Sci. 78 (2000) 23]; [Biochem. Biophys. Res. Commun. 272 (2000) 629]; [FEBS Lett. 476 (2000) 113]; [Thermochim. Acta 378 (2001) 35], the molecular mechanism for rotation of the c-rotor and the subsequent rotation of the c-subunit and the c-subunit has been proposed. The details of the elementary steps involved in ion translocation and energy conversion in the F0 portion ofATP synthase have been provided. Electrostatic effects drive the rotation of the c-subunits in steps of 15◦ each during proton binding as well as unbinding. During the rotation of the c-rotor, the energy of the ion gradients is transiently stored as twist in the c-subunits, and finally as torsional strain in the c-subunit. The mechanism has been shown to be consistent with a general kinetic analysis of ATP synthesis by ATP synthase. The detailed molecular mechanism compels a paradigm shift from chemiosmotic dogma (where the membrane simply acts as an insulator and only energized aqueous media are permissible) towards a view where molecular interactions between ion and protein-in-the-membrane are critical for elementary steps involving transduction, storage and utilization of the energy of the ion gradients.