The mechanism of action of valinomycin on the thylakoid membrane : Characterization of the electric current density.

Most of the studies devoted to the mechanism by which certain antibiotics increase the ion permeability ofbiological membranes have been carried out on artificialmodel systems. Undoubtedly one of the major reasons for this was that some of the most relevant biological membrane systems are of submicroscopic dimensions and thus inaccessible to the common electrochemical measuring techniques. This holds for the inner membrane systems of chloroplasts, mitochondria, and retinal rods.Since it is not trivial that a mechanism of action found for a model membrane works as well in a biological one with a much higher structural complexity, it seemed worth-while to study the mechanism of action of ionophorous antibiotics on the above-mentioned biological membranes.In this paper, a nonelectrochemical method for measuring both the voltage and the current across the inner chloroplast membrane (or thylakoid membrane) is established in extension of earlier work. This method is used to characterize the mode of action of valinomycin on the thylakoid membrane.