Double-inhibitor and uncoupler-inhibitor-titrations. 2. Analysis with a nonlinear model of chemiosmotic energy coupling

Abstract

The results of double-inhibitor and uncoupler-inhibitor titrations have been simulated and analyzed with a nonlinear model of delocalized protonic coupling obtained by linking two proton pump models of the kind studied by Pietrobon and Caplan [Pietrobon, D., and Caplan, S. R. (1985) Biochemistry 24, 5764-5776] through their common intermediate .DELTA.~.mu.H. It is shown that the results predicted by a delocalized chemiosmotic model are highly dependent on the kind of relationships existing between rate of ATP synthesis, Jp, and .DELTA.~.mu.H and rate of electron transfer, Je, and .DELTA.~.mu.H. With nonlinear flow-force relationships all the results reported so far are not neceassarily inconsistent with the delocalized chemiosmotic model provided that the relationships between rates and .DELTA.~.mu.H satisfy the following requirements: .vdelta.Jp/.vdelta..DELTA.~.mu.H increases and/or .vdelta.Je/.vdelta..DELTA.~.mu.H decreases as .DELTA.~.mu.H increases.