Thiol modulation of the chloroplast ATP synthase is dependent on the energization of thylakoid membranes

Plant Cell Physiol. 2012 Apr;53(4):626-34. doi: 10.1093/pcp/pcs018. Epub 2012 Feb 22.


Thiol modulation of the chloroplast ATP synthase γ subunit has been recognized as an important regulatory system for the activation of ATP hydrolysis activity, although the physiological significance of this regulation system remains poorly characterized. Since the membrane potential required by this enzyme to initiate ATP synthesis for the reduced enzyme is lower than that needed for the oxidized form, reduction of this enzyme was interpreted as effective regulation for efficient photophosphorylation. However, no concrete evidence has been obtained to date relating to the timing and mode of chloroplast ATP synthase reduction and oxidation in green plants. In this study, thorough analysis of the redox state of regulatory cysteines of the chloroplast ATP synthase γ subunit in intact chloroplasts and leaves shows that thiol modulation of this enzyme is pivotal in prohibiting futile ATP hydrolysis activity in the dark. However, the physiological importance of efficient ATP synthesis driven by the reduced enzyme in the light could not be demonstrated. In addition, we investigated the significance of the electrochemical proton gradient in reducing the γ subunit by the reduced form of thioredoxin in chloroplasts, providing strong insights into the molecular mechanisms underlying the formation and reduction of the disulfide bond on the γ subunit in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chloroplast Proton-Translocating ATPases / metabolism*
  • Chloroplasts / enzymology
  • Chloroplasts / metabolism
  • Oxidation-Reduction
  • Plant Leaves / enzymology
  • Plant Leaves / metabolism
  • Plant Proteins / metabolism
  • Spinacia oleracea / enzymology
  • Spinacia oleracea / metabolism
  • Thylakoids / metabolism*


  • Plant Proteins
  • Chloroplast Proton-Translocating ATPases