Anion (and cation) requirements of the coupled electron flow in spinach thylakoids.

Proton uptake as well as coupled electron flow of chloroplasts swollen in dilute impermeable buffers became dependent upon the addition of exogenous permeable anions. This dependence was observed with both cyclic and noncyclic electron acceptors, suggesting that this anion requirement is associated with the electrogenic proton uptake step rather than with the oxygen-evolving reactions of photosystem II.