Light-driven quinone reduction in heliobacterial membranes
Journal Article
·
· Photosynthesis Research
- Arizona State Univ., Tempe, AZ (United States); Arizona State University
- Arizona State Univ., Tempe, AZ (United States)
- Arizona State Univ., Tempe, AZ (United States); Univ. of Wisconsin, Madison, WI (United States)
We report that 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 modi- fied 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. Therefore, the HbRC may represent a functional evolutionary intermediate between PSI and the Type II RCs.
- Research Organization:
- Arizona State Univ., Tempe, AZ (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
- Grant/Contract Number:
- SC0010575
- OSTI ID:
- 1494565
- Journal Information:
- Photosynthesis Research, Journal Name: Photosynthesis Research Journal Issue: 1 Vol. 138; ISSN 0166-8595
- Publisher:
- SpringerCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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OSTI ID:1494566