Hydrostatic Pressure as a Tool to Study F-type ATPsynthases

Abstract

We are using Hydrostatic Pressure as a tool to study the kinetics of substrate hydrolysis by the soluble chloroplast ATPsynthase (CF₀F₁). We show that pressurization differentially affects the hydrolysis of ATP and the pseudosubstrates p-nitrophenylphosphate and 3-O-methyl-fluoresceinphosphate. An activation volume of -23.7 ml·mol⁻¹ was calculated for the ATPase reaction. Pressurization of the CF₀F₁, followed by depressurization, impairs ATPase independently of inducing a clear dissociation of catalytic subunits. This does not impair 3OMFPase activity. Addition of glycerol to the pressurization medium helped to preserve protein structure and activity under pressure. Addition of ethanol, while activating the protein, contributed to destabilize the oligomer to pressure effects. Further studies with hydrostatic pressure dissociation could indicate the relevance of subunit contacts for the mechanisms of rotational multi-site and single-site catalysis.