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

Controlling Redox Enzyme Orientation at Planar Electrodes

“…Depending on the environment or on the type of microorganism, one protein can replace another one as electron donor or acceptor for a specific process. Photosynthesis is one relevant example for which the involvement of one protein over another varies depending on the considered species (such as algae, cyanobacteria, or plants) [1]. Heme-(cytochrome c6) or copper-containing proteins (plastocyanin), on the one hand, and FeS cluster-or flavin mononucleotide-containing proteins (flavodoxin), on the other hand, act as electron transfer shuttles allowing the coupling of water oxidation to NADP + reduction by photosystem I/photosystem II systems.…”

The Synthetic Biology Toolkit for Photosynthetic Microorganisms

“…Their unique combination of characteristics, including relatively fast photosynthetic growth, availability of redox power, a plethora of internal membranes, and subcellular microcompartments, opens up a completely new palette of synthetic biology strategies that is not possible in other well-studied heterotrophic host organisms. The photosynthetic machinery is full of interesting targets for synthetic biology strategies (Leister, 2019), such as enhancing photosynthesis for increased biomass production and yield (Zhu et al, 2010), direct coupling of metabolic pathways to photosynthetic reducing power (Mellor et al, 2017), and creation of bio-nano hybrids where photosynthetic modules are used as a source of electrons for nonbiological processes by linking them to abiotic catalysts or electrode nanomaterials (Saar et al, 2018) or by derivatization of photosynthetic electrons by redox mediators (Longatte et al, 2015;Fu et al, 2017). Although in principle such applications can be hosted in plants, photosynthetic microorganisms offer distinct advantages: the combination of photosynthesis with simple unicellular organization, facile genetic manipulation strategies, quick growth in liquid cultures, relative ease of scale-up, and, if grown in contained facilities, potentially fewer regulatory challenges.…”

“…This means that their photosynthetic membranes and photosystems therein are more accessible to heterologous proteins. This has enabled the direct linkage of photosynthesis with heterologous metabolic reactions (direct light-driven synthesis) by expression of electron-consuming enzymes (cytochromes P450) in the thylakoid membranes (Berepiki et al, 2016;Wlodarczyk et al, 2016;Mellor et al, 2017). A drawback of the extensive membrane system in cyanobacteria is that our understanding of metabolic regulation through their intermingling respiratory and photosynthetic electron transport chains is incomplete.…”

Harnessing transcription for bioproduction in cyanobacteria

“…Cyanobacteria contain specialized carbon‐concentrating compartments that increase carbon fixation efficiency, but can also be used as a scaffold to target biosynthetic enzymes to create specialized metabolic microcompartments (Gonzalez‐Esquer et al ). Moreover, cyanobacteria can photosynthetically generate and efficiently distribute redox power to fuel redox‐dependent heterologous pathways, due to the plasticity of the photosynthetic electron carrier proteins (Mellor et al ). Many cyanobacterial species fix atmospheric nitrogen and thus the need for nitrogen supplementation is limited.…”

“…Moreover, cyanobacteria can photosynthetically generate and efficiently distribute redox power to fuel redox-dependent heterologous pathways, due to the plasticity of the photosynthetic electron carrier proteins Abbreviations -RNAP, RNA polymerase. (Mellor et al 2017). Many cyanobacterial species fix atmospheric nitrogen and thus the need for nitrogen supplementation is limited.…”