The effect of gramicidin on ATP synthesis in pea chloroplasts: two modes of phosphorylation

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Abstract
The effect of gramicidin on the phosphorylation rate, electron flow and light‐induced H2+ uptake (ΔH+) in chloroplasts with methyl viologen (MV) or phenazine methosulfate (PMS) added has been studied. In the presence of MV low concentrations of gramicidin (~10−9 M) were shown to inhibit the phosphorylation rate up to 80–90% of the initial value, without changing either the electron transport rate or ΔH+ value. Two components of phosphorylation have been identified in the presence of PMS ‐ the first is DCMU‐sensitive, which was suppressed by low gramicidin concentrations (< 10−9 M) and the second ‐ DCMU‐insensitive component, which was suppressed by high gramicidin concentrations (~10−7 M) exclusively, the high gramicidin concentration inducing the ΔH+ value fo fall.