Researchers are puzzling over a widespread vitamin B shortage that appears to be killing wildlife.
Image courtesy of Lennart Balk and Per-Åke Hägerroth (Stockholm University, Stockholm).
New Research In
Physical Sciences
Featured Portals
Articles by Topic
Biological Sciences
Featured Portals
Articles by Topic
Edited by Harry B. Gray, California Institute of Technology, Pasadena, CA, and approved February 1, 2013 (received for review December 19, 2012)
Abstract
As much as two-thirds of the proton gradient used for transmembrane free energy storage in oxygenic photosynthesis is generated by the cytochrome b6f complex. The proton uptake pathway from the electrochemically negative (n) aqueous phase to the n-side quinone binding site of the complex, and a probable route for proton exit to the positive phase resulting from quinol oxidation, are defined in a 2.70-Å crystal structure and in structures with quinone analog inhibitors at 3.07 Å (tridecyl-stigmatellin) and 3.25-Å (2-nonyl-4-hydroxyquinoline N-oxide) resolution. The simplest n-side proton pathway extends from the aqueous phase via Asp20 and Arg207 (cytochrome b6 subunit) to quinone bound axially to heme cn. On the positive side, the heme-proximal Glu78 (subunit IV), which accepts protons from plastosemiquinone, defines a route for H+ transfer to the aqueous phase. These pathways provide a structure-based description of the quinone-mediated proton transfer responsible for generation of the transmembrane electrochemical potential gradient in oxygenic photosynthesis.
Footnotes
- ↵1To whom correspondence should be addressed. E-mail: waclab{at}purdue.edu.
Author contributions: W.A.C. designed research; S.S.H., E.Y., and D.B. performed research; W.A.C. contributed new reagents/analytic tools; S.S.H., E.Y., D.B., and W.A.C. analyzed data; and S.S.H. and W.A.C. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The atomic coordinates and structure factors have been deposited in the Protein Data Bank, www.pdb.org [PDB ID codes 4H44 (native cyt b6f structure), 4H13 (tridecyl-stigmatellin–containing structure), and 4H0L (2-nonyl-4-hydroxyquinoline N-oxide–containing structure)].
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1222248110/-/DCSupplemental.
Proton transfer by cytochrome b6f
More Articles of This Classification
Biological Sciences
Biophysics and Computational Biology
Related Content
Cited by...
- Structure of the plant photosystem I
- Protein Degradation Rate in Arabidopsis thaliana Leaf Growth and Development
- Trans-membrane Signaling in Photosynthetic State Transitions: REDOX- AND STRUCTURE-DEPENDENT INTERACTION IN VITRO BETWEEN STT7 KINASE AND THE CYTOCHROME b6f COMPLEX
- Why chloroplasts and mitochondria retain their own genomes and genetic systems: Colocation for redox regulation of gene expression
- Activation of cyclic electron flow by hydrogen peroxide in vivo
- Functional Characterization of the Small Regulatory Subunit PetP from the Cytochrome b6f Complex in Thermosynechococcus elongatus
Similar Articles
You May Also be Interested in
Robert Reed explains genetic controls on butterfly wing colors.
Better understanding how the truffles reproduce has major implications for farmers, chefs, and foodies enamored with the expensive, pungent fungus.
Image courtesy of Shutterstock/Vitalina Rybakova.
PNAS QnAs with NAS foreign associate and metabolic engineer Sang Yup Lee
Researchers report a species of early bird with a combination of bird-like and dinosaur-like bone morphologies, and the structure of the bird’s shoulder girdle highlights the role of developmental plasticity in the early evolution of birds, according to the authors.
