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High-resolution cryo-EM structures of plant cytochrome b 6 f at work.

Marcin SarewiczMateusz SzwalecSebastian PintscherPaulina IndykaMichal RawskiRafał PietrasBohun MieleckiLukasz KoziejMarcin JaciukSebastian GlattArtur Osyczka
Published in: Science advances (2023)
Plants use solar energy to power cellular metabolism. The oxidation of plastoquinol and reduction of plastocyanin by cytochrome b 6 f (Cyt b 6 f) is known as one of the key steps of photosynthesis, but the catalytic mechanism in the plastoquinone oxidation site (Q p ) remains elusive. Here, we describe two high-resolution cryo-EM structures of the spinach Cyt b 6 f homodimer with endogenous plastoquinones and in complex with plastocyanin. Three plastoquinones are visible and line up one after another head to tail near Q p in both monomers, indicating the existence of a channel in each monomer. Therefore, quinones appear to flow through Cyt b 6 f in one direction, transiently exposing the redox-active ring of quinone during catalysis. Our work proposes an unprecedented one-way traffic model that explains efficient quinol oxidation during photosynthesis and respiration.
Keyphrases
  • high resolution
  • electron transfer
  • hydrogen peroxide
  • visible light
  • mass spectrometry
  • air pollution
  • tandem mass spectrometry
  • high speed
  • optic nerve
  • plant growth