PGRL1 is the elusive ferredoxin-plastoquinone reductase in photosynthetic cyclic electron flow

Mol Cell. 2013 Feb 7;49(3):511-23. doi: 10.1016/j.molcel.2012.11.030. Epub 2013 Jan 3.


During plant photosynthesis, photosystems I (PSI) and II (PSII), located in the thylakoid membranes of the chloroplast, use light energy to mobilize electron transport. Different modes of electron flow exist. Linear electron flow is driven by both photosystems and generates ATP and NADPH, whereas cyclic electron flow (CEF) is driven by PSI alone and generates ATP only. Two variants of CEF exist in flowering plants, of which one is sensitive to antimycin A (AA) and involves the two thylakoid proteins, PGR5 and PGRL1. However, neither the mechanism nor the site of reinjection of electrons from ferredoxin into the thylakoid electron transport chain during AA-sensitive CEF is known. Here, we show that PGRL1 accepts electrons from ferredoxin in a PGR5-dependent manner and reduces quinones in an AA-sensitive fashion. PGRL1 activity itself requires several redox-active cysteine residues and a Fe-containing cofactor. We therefore propose that PGRL1 is the elusive ferredoxin-plastoquinone reductase (FQR).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / enzymology*
  • Arabidopsis / physiology*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / metabolism*
  • Conserved Sequence
  • Cysteine / metabolism
  • Electron Transport
  • Ferredoxins / metabolism*
  • Iron / metabolism
  • Membrane Proteins / chemistry
  • Membrane Proteins / metabolism*
  • Models, Biological
  • Molecular Sequence Data
  • Mutant Proteins / chemistry
  • Mutant Proteins / metabolism
  • Oxidation-Reduction
  • Photosynthesis*
  • Protein Binding
  • Protein Multimerization
  • Protein Stability
  • Quinone Reductases / metabolism*
  • Recombinant Proteins / metabolism
  • Thioredoxins / metabolism
  • Thylakoids / metabolism


  • Arabidopsis Proteins
  • Ferredoxins
  • Membrane Proteins
  • Mutant Proteins
  • PGRL1 protein, Arabidopsis
  • Recombinant Proteins
  • Thioredoxins
  • Iron
  • Quinone Reductases
  • sulfide quinone reductase
  • Cysteine