Light-induced proton slip and proton leak at the thylakoid membrane

• Published in: Journal of plant physiology Vol. 161; no. 12; pp. 1325 - 1337
• Main Authors: Richter, Michael, Daufenbach, Jens, Drebing, Stefanie, Vucetic, Verena, Nguyen, Duc Tung
• Format: Journal Article
• Language: English
• Published: Jena Elsevier GmbH 01.12.2004; Elsevier; Elsevier Science Ltd
• Subjects: Biological and medical sciences; Cell physiology; CF1-γ; Chloroplast Proton-Translocating ATPases - metabolism; Dithiothreitol - pharmacology; Electron Transport - drug effects; Electron Transport - physiology; Fluorescence labeling of proteins; Fundamental and applied biological sciences. Psychology; H+/e; ion transport; Light; Photophosphorylation - physiology; Photosynthesis - physiology; physiological transport; Plant Leaves - metabolism; plant physiology; Plant physiology and development; Plasma membrane and permeation; Proton leak; Proton slip; Protons; spinach; Spinacia oleracea; Spinacia oleracea - metabolism; Thylakoid uncoupling; thylakoids; Thylakoids - metabolism; vegetable crops; Fluorescence labeling of proteins; Proton leak; CF1-γ; DTT; Chl; MV; Spinacia oleracea; Thylakoid uncoupling; IAF; FeCy; H+/e; Proton slip; PPFD; Enzyme; Plant leaf; Synthase; Thioredoxin; Thylakoid; Chenopodiaceae; Dicotyledones; Angiospermae; Spermatophyta; Kinetics; ATP
• ISSN: 0176-1617; 1618-1328
• DOI: 10.1016/j.jplph.2004.03.007

A treatment of leaves of Spinacia oleracea L. with light or with the thiol reagent dithiothreitol in the dark led to partly uncoupled thylakoids. After induction in intact leaves, the partial uncoupling was irreversible at the level of isolated thylakoids. We distinguish between uncoupling by proton slip, which means a decrease of the H+/e−-ratio due to less efficient proton pumping, and proton leak as defined by enhanced kinetics of proton efflux. Proton slip and proton leak made about equal contributions to the total uncoupling. The enhanced proton efflux kinetics corresponded to reduction of subunit CF1-γ of the ATP synthase as shown by fluorescence labeling of thylakoid proteins with the sulfhydryl probe 5-iodoacetamido fluorescein. The maximum value of the fraction of reduced CF1-γ was only 36%, which indicates that in vivo the reduction of CF1-γ could be limited by fast reoxidation and/or restricted accessibility of CF1-γ to thioredoxin. Measurements of the ratio ATP/2e indicated that only the uncoupling related to less efficient proton pumping led to a decrease in the ATP yield.