Localized Proton Domains in pH-Dependent Control of Photosynthetic Electron Transport under the Influence of Lipophilic Tertiary Amines

  • Angela Janowitz
  • Gabriele Günther
  • Henrik Laasch


Photosynthetic electron transport is under control of the intrathylakoid proton potential,µ͂HI (1,2). When µ͂HI increases in the light, with the build-up of a transthylakoid proton gradient (Δ µ͂H), electron flow is decelerated. Two major sites of µHI-dependent feed-back control have been discussed: the reduction of the primary photosystem (PS) II acceptor QA (2) and the oxidation of plastohydroquinone at the cytochrome b/f complex (1). Under condition of photophosphorylation/µ͂H decreases and flow control is partly released. Recently, lipophilic tertiary amines were shown to be effective inhibitors of ATP synthesis and of the build-up of Δ µ͂H (3–5). The inhibition of a Δ µ͂H rise, as indicated by 9-aminoacridine (9-AA) fluorescence quenching (6) or (l4C)-methylamine uptake (7), appeared to be determinant for the decline of photophosphorylation. In this, the effects of lipophilic amines resemble ‘classical’ uncoupler effects. Nevertheless, the pH-dependent flow control was preserved in the presence of tertiary amines despite of the low Δ µ͂H observed. Control mechanisms were active although µ͂HI appeared to be low. This is in apparent contradiction to the theory of pH-dependent flow control.


Electron Flow Tertiary Amine Photosynthetic Electron Transport Uncoupler Effect Proton Uptake 
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Copyright information

© Springer Science+Business Media New York 1990

Authors and Affiliations

  • Angela Janowitz
    • 1
  • Gabriele Günther
    • 1
  • Henrik Laasch
    • 1
  1. 1.Botanisches InstitutHeinrich-Heine-UniversitätDüsseldorf 1Germany

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