Elucidating the role of primary and secondary sphere Zn ligands in the cyanobacterial CO uptake complex NDH-1: The essentiality of arginine in zinc coordination and catalysis.

Inorganic carbon uptake in cyanobacteria is facilitated by an energetically intensive CO-concentrating mechanism (CCM). Specialized Type-1 NDH complexes function as a part of this mechanism to couple photosynthetic energy generated by redox reactions of the electron transport chain (ETC) to CO hydration. This active site of CO hydration incorporates an arginine side chain as a Zn ligand, diverging from the typical histidine and/or cysteine residues found in standard CAs.

Cyanobacterial Bioenergetics in Relation to Cellular Growth and Productivity.

Cyanobacteria, the evolutionary originators of oxygenic photosynthesis, have the capability to convert CO, water, and minerals into biomass using solar energy. This process is driven by intricate bioenergetic mechanisms that consist of interconnected photosynthetic and respiratory electron transport chains coupled. Over the last few decades, advances in physiochemical analysis, molecular genetics, and structural analysis have enabled us to gain a more comprehensive understanding of cyanobacterial bioenergetics.

Cyclic Electron Flow-Coupled Proton Pumping in sp. PCC6803 Is Dependent upon NADPH Oxidation by the Soluble Isoform of Ferredoxin:NADP-Oxidoreductase.

Ferredoxin:NADP-oxidoreductase (FNR) catalyzes the reversible exchange of electrons between ferredoxin (Fd) and NADP(H). Reduction of NADP by Fd via FNR is essential in the terminal steps of photosynthetic electron transfer, as light-activated electron flow produces NADPH for CO assimilation. FNR also catalyzes the reverse reaction in photosynthetic organisms, transferring electrons from NADPH to Fd, which is important in cyanobacteria for respiration and cyclic electron flow (CEF).

From manganese oxidation to water oxidation: assembly and evolution of the water-splitting complex in photosystem II.

The manganese cluster of photosystem II has been the focus of intense research aiming to understand the mechanism of HO-oxidation. Great effort has also been applied to investigating its oxidative photoassembly process, termed photoactivation that involves the light-driven incorporation of metal ions into the active MnCaO cluster. The knowledge gained on these topics has fundamental scientific significance, but may also provide the blueprints for the development of biomimetic devices capable of splitting water for solar energy applications.

Bioenergetics: To the dark side and back with cyanobacterial ATP synthase.

FF ATP synthases are remarkable because of their strict reversibility and the diverse mechanisms that prevent back reactions and futile cycling. Cyanobacteria power both the photosynthetic and respiratory electron transport chains in the same membrane system using a novel regulatory polypeptide that is expressed only at night.