The efficiency of energized protons for ATP synthesis depends on the membrane topography in thylakoids

Abstract

In thylakoids system II water‐splitting proton generation is mainly localized in grana stacks, whereas system I plastoquinol reoxidation, is essentially restricted to non‐appressed regions, such as stromal lamellae; the same is true for the coupling factor. For a given mean proton gradient, a system II chain was found to be less able to drive phosphorylation than a system I or a system I + II chain. These results support our microchemiosmotic hypothesis, based on the existence of lateral resistances to H + movements. They confirm that the proton gradients at the redox chain and at the coupling factor are unequal and that both are different from their mean experimentally measured value.