Contribution of ΔpH and ΔE to photosynthesis of Chlamydomonas reinhardtii

Abstract

The contribution of two components (ΔpH and ΔE) of the proton motive force to photosynthesis of C. reinhardtii was studied. Valinomycin, a photophosphorylation uncoupler, decreased significantly the fast phase (related mainly to the membrane electric potential) of millisecond delayed light emission (ms-DLE) of C. reinhardtii. Nigericin, another photophosphorylation uncoupler, decreased the slow phase (related mainly to the proton gradient) and partly also the fast phase of ms-DLE. Both valinomycin and nigericin decreased the net ATP content and photosynthetic rate of C. reinhardtii, but the inhibition by nigericin was stronger than that by valinomycin. Hence both components of the proton motive force contribute to photosynthesis and although the contribution of ΔpH is larger than that of ΔE, the latter is not negligible in photosynthesis of C. reinhardtii.