A computational investigation of the intrinsic electric field of ATP synthase

Abstract

Mitchell’s chemiosmotic theory stipulates that an electrochemical gradient of protons across the inner mitochondrial membrane provides the free energy for the biosynthesis of adenosine 5’-triphosphate (ATP). This proton gradient generates an electric field of ~ 10⁷ V∙m^-1. It is hypothesized that ATP synthase, the enzyme catalyzing ATP synthesis, itself generates a field/potential comparable to that of the proton gradient. A programme, PrES, was developed to compute the intrinsic field/potential of ATP synthase (or that of any protein). The calculated field/potential by PrES is based on AMBER charges and is found to be of sufficient accuracy within the biological context. The intrinsic field of ATP synthase is found to be of strengths 10⁶ - 10⁸ V∙m^-1 around the protein and is associated with a voltage of ~ 70 mV between its extremities. This potential difference adds a ΔG of around -7 kJ (per mol of protons), a significant correction as hypothesized