NREL Scientists Find Key Function for Ferredoxins in Algae Hydrogen Production
Scientists at the Energy Department’s National Renewable Energy Laboratory have demonstrated that just two of six iron-sulfur-containing ferredoxins in a representative species of algae promote electron transfers to and from hydrogenases. The finding suggests ways to increase the production of hydrogen by algae, which could help turn hydrogen into a viable alternative fuel for transportation.
A paper on the discovery, “Identification of global ferredoxin interaction networks in in Chlamydomonas reinhardtii,” appears online in The Journal of Biological Chemistry. The authors note that Chlamydomonas reinhardtii contains six chloroplast-localized ferredoxins (the iron-sulfur-containing redox mediators) whose exact functions are still unclear. C. reinhardtii often serves as a model for other algae strains because its genome is sequenced and it is amenable to genetic modification.
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By analyzing the interacting partners and reactions catalyzed by each of the six ferredoxins (FDX), they found that FDX1 serves as the primary electron donor to hydrogen production via photosynthesis. FDX2 can do the job, but at less than half the rate, while FDX3 through FDX6 appear to play no role in this particular reaction.
In technical terms, the NREL scientists deconvoluted the complex network of redox reactions centered in the six iron-sulfur-containing algal ferredoxins. By revealing that only two of them promote electron transfer to and from hydrogenases, they helped extend the understanding of electron competition at the level of the ferredoxin.
“When we tested all the ferredoxins as electron donors, the best rate was obtained with FDX1,” said NREL Scientist Alexandra Dubini, one of the authors for the paper. Lead authors are Erin Peden and Marko Boem, with contributions from NREL colleagues David Mulder, ReAnna Davis, William Old, Paul King, Maria Ghirardi and Dubini.
The discovery could lead to ways to stem the flow of electrons to the other pathways, forcing more electrons through the FDX1 pathway for increased hydrogen production, Dubini said. “There is this competition for photosynthetic reductant among different pathways and ferredoxins distribute electrons among the various other pathways, depending on the conditions and requirements of the cell.”
Source: http://www.nrel.gov/news/press/2014/8301.html
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