Light-driven quinone reduction in heliobacterial membranes

Trevor S. Kashey, Dustin D. Luu, John C. Cowgill, Patricia L. Baker, Kevin Redding

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Photosynthetic reaction centers (RCs) evolved > 3 billion years ago and have diverged into Type II RCs reducing quinones and Type I RCs reducing soluble acceptors via iron–sulfur clusters. Photosystem I (PSI), the exemplar Type I RC, uses modified menaquinones as intermediate electron transfer cofactors, but it has been controversial if the Type I RC of heliobacteria (HbRC) uses its two bound menaquinones in the same way. The sequence of the quinone-binding site in PSI is not conserved in the HbRC, and the recently solved crystal structure of the HbRC does not reveal a quinone in the analogous site. We found that illumination of heliobacterial membranes resulted in reduction of menaquinone to menaquinol, suggesting that the HbRC can perform a function thought restricted to Type II RCs. Experiments on membranes and live cells are consistent with the hypothesis that the HbRC preferentially reduces soluble electron acceptors (e.g., ferredoxins) in low light, but switches to reducing lipophilic quinones in high light, when the soluble acceptor pool becomes full. Thus, the HbRC may represent a functional evolutionary intermediate between PSI and the Type II RCs.

Original languageEnglish (US)
Pages (from-to)1-9
Number of pages9
JournalPhotosynthesis research
Issue number1
StatePublished - Oct 1 2018


  • Heliobacteria
  • Quinone
  • Reaction centers
  • Type I reaction center
  • Type II reaction center

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology


Dive into the research topics of 'Light-driven quinone reduction in heliobacterial membranes'. Together they form a unique fingerprint.

Cite this