Function and Regulation of Ferredoxins in the Cyanobacterium, Synechocystis PCC6803: Recent Advances

Abstract

Ferredoxins (Fed), occurring in most organisms, are small proteins that use their iron-sulfur cluster to distribute electrons to various metabolic pathways, likely including hydrogen production. Here, we summarize the current knowledge on ferredoxins in cyanobacteria, the prokaryotes regarded as important producers of the oxygenic atmosphere and biomass for the food chain, as well as promising cell factories for biofuel production. Most studies of ferredoxins were performed in the model strain, Synechocystis PCC6803, which possesses nine highly-conserved ferredoxins encoded by monocistronic or operonic genes, some of which are localized in conserved genome regions. Fed1, encoded by a light-inducible gene, is a highly abundant protein essential to photosynthesis. Fed2-Fed9, encoded by genes differently regulated by trophic conditions, are low-abundant proteins that play prominent roles in the tolerance to environmental stresses. Concerning the selectivity/redundancy of ferredoxin, we report that Fed1, Fed7 and Fed9 belong to ferredoxin-glutaredoxin-thioredoxin crosstalk pathways operating in the protection against oxidative and metal stresses. Furthermore, Fed7 specifically interacts with a DnaJ-like protein, an interaction that has been conserved in photosynthetic eukaryotes in the form of a composite protein comprising DnaJ- and Fed7-like domains. Fed9 specifically interacts with the Flv3 flavodiiron protein acting in the photoreduction of O2 to H2O.

Interplay of SpkG kinase and the Slr0151 protein in the phosphorylation of ferredoxin 5 in Synechocystis sp. strain PCC 6803

“…showed that slr0151 and slr0152 are transcribed separately from the upstream genes, possibly as bicistronic mRNA. Among other proteins, the slr0144–slr0152 gene cluster encodes the Slr0148 protein which has been recently annotated as ferredoxin 5 (Fd5) and shown to be a phosphoprotein, with modified T18 and T72 residues . Here, we demonstrate a relationship between phosphorylation of Fd5 and the SpkG kinase which was revealed by investigation of the Δslr0152(ΔspkG) mutant of Synechocystis 6803 with the targeted proteomic approach (the selected reaction monitoring, SRM).…”

Photosynthetic fuel for heterologous enzymes: the role of electron carrier proteins

“…This permits the reduction of NADP + to NADPH (−320 mV) and allows them to act as a hub distributing electrons towards central metabolic reactions in plants and cyanobacteria [reviewed by (Hanke and Mulo 2013;Cassier-Chauvat and Chauvat 2014;Goss and Hanke 2014)]. Ferredoxin also plays a key role in cyclic electron transport, which balances the production of ATP and NADPH by recycling electrons through the plastoquinone pool and the cytochrome b 6 f complex (Yamori and Shikanai 2016).…”

“…Ferredoxin also plays a key role in cyclic electron transport, which balances the production of ATP and NADPH by recycling electrons through the plastoquinone pool and the cytochrome b 6 f complex (Yamori and Shikanai 2016). Photosynthetic organisms have several ferredoxin isoforms, with distinct roles (Hanke et al 2004;Cassier-Chauvat and Chauvat 2014). Their central role in distributing reducing power Arrows indicate linear electron transport during photosynthetic activity, starting with the oxidation of water and ending with the reduction of NADP + to NADPH.…”

“…3) constitutes a major challenge. While the primary electron sinks-such as NADP + photoreductionare relatively well understood, recent proteomic studies on ferredoxin interaction partners of Synechocystis and Chlamydomonas ferredoxins have identified ~200 possible ferredoxin-dependent proteins (Hanke et al 2011;Peden et al 2013;Cassier-Chauvat and Chauvat 2014). This highlights the incompleteness of our knowledge of ferredoxin-dependent processes and underlines the importance of competitiveness for heterologous enzymes.…”

Prochlorococcusphage ferredoxin: structural characterization and electron transfer to cyanobacterial sulfite reductases

“…The Prochlorococcus P-SSM2 phage Fd (pssm2-Fd) supports the reduction of phage phycoerythrobilin synthase (PebS), which catalyzes the reduction of biliverdin IXα to 3E/3Z phycoerythrobilin (27,28). While prior studies showed that some Fds support ET to diverse partner oxidoreductases (29)(30)(31)(32), it remains unclear how the biophysical properties of this and other phage Fds compare to host Fds, which can function as ET hubs that couple light harvesting to a range of reductive metabolic reactions (31)(32)(33). In addition, it is not known how the specific constraints of viral evolution might have modulated the primary structure and partner specificity of phage Fd.…”