ATP synthase: what we know about ATP hydrolysis and what we do not know about ATP synthesis

In ATP synthase. X-ray structures, demonstration of ATP-driven gamma-subuni t rotation, and tryptophan fluorescence techniques to determine catalytic s ite occupancy and nucleotide binding affinities have resulted in pronounced progress in understanding ATP hydrolysis, for which a mechanism is present ed here. In contrast, ATP synthesis remains enigmatic. The molecular mechan ism by which ADP is bound in presence of a high ATP/ADP concentration ratio is a fundamental unknown: similarly P-i binding is not understood. Techniq ues to measure catalytic site occupancy and ligand binding affinity changes during net ATP synthesis are much needed. Relation of these parameters to gamma-rotation is a further goal. A speculative model for ATP synthesis is offered. (C) 2000 Elsevier Science B.V. All rights reserved.