Johnson, M.P. and Ruban, A.V. (2014) Rethinking the existence of a steady-state Delta psi component of the proton motive force across plant thylakoid membranes. Photosynthesis Research, 119 (1-2). 233 - 242. ISSN 0166-8595
Abstract
Light-driven photosynthetic electron transport is coupled to the movement of protons from the chloroplast stroma to the thylakoid lumen. The resulting proton motive force that is generated is used to drive the conformational rotation of the transmembrane thylakoid ATPase enzyme which converts ADP (adenosine diphosphate) and Pi (inorganic phosphate) into ATP (adenosine triphosphate), the energy currency of the plant cell required for carbon fixation and other metabolic processes. According to Mitchell’s chemiosmotic hypothesis, the proton motive force can be parsed into the transmembrane proton gradient (ΔpH) and the electric field gradient (Δψ), which are thermodynamically equivalent. In chloroplasts, the proton motive force has been suggested to be split almost equally between Δψ and ΔpH (Kramer et al., Photosynth Res 60:151–163, 1999). One of the central pieces of evidence for this theory is the existence of a steady-state electrochromic shift (ECS) absorption signal detected ~515 nm in plant leaves during illumination. The interpretation of this signal is complicated, however, by a heavily overlapping absorption change ~535 nm associated with the formation of photoprotective energy dissipation (qE) during illumination. In this study, we present new evidence that dissects the overlapping contributions of the ECS and qE-related absorption changes in wild-type Arabidopsis leaves using specific inhibitors of the ΔpH (nigericin) and Δψ (valinomycin) and separately using leaves of the Arabidopsis lut2npq1 mutant that lacks qE. In both cases, our data show that no steady-state ECS signal persists in the light longer than ~60 s. The consequences of our observations for the suggesting parsing of steady-state thylakoid proton motive force between (ΔpH) and the electric field gradient (Δψ) are discussed.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2014 Springer. This is an author produced version of a paper subsequently published in Photosynthesis Research. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Proton motive force; Electron transport; ATP synthesis; Electrochromic shift; Non-photochemical quenching |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Biosciences (Sheffield) > Department of Molecular Biology and Biotechnology (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 16 Jun 2014 13:10 |
Last Modified: | 15 Nov 2016 23:48 |
Published Version: | http://dx.doi.org/10.1007/s11120-013-9817-2 |
Status: | Published |
Publisher: | Springer |
Refereed: | Yes |
Identification Number: | 10.1007/s11120-013-9817-2 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:79364 |