COV is the standard word for coronavirus. FeFe is a hydrogenase, in biochemistry its an enzyme used in a catalyzing process that involves hydrogen molecules. Essentially, FeFe has been used in processes for the creation of bactrium, RNA or viral strands.

NCBI (2015):  “Engineering Artificial Machines from Designable DNA Materials for Biomedical Applications”

Unlike most DNA structure building processes, the RNA structures were built in a complete isothermal process at 37°C. Interestingly, with tethering [FeFe]-hydrogenase and ferredoxin catalyzes in the adjacent position through a specific RNA aptamer–protein interaction on the RNA structure, in vivo hydrogen production efficiency was improved significantly compared to cell carrying free enzymes
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4442581/

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Related:
(WIKI)  Hydrogenase
Until 2004, the [Fe]-only hydrogenase was believed to be “metal-free”. Then, Thauer et al. showed that the metal-free hydrogenases in fact contain iron atom in its active site. As a result, those enzymes previously classified as “metal-free” are now named [Fe]-only hydrogenases. This protein contains only a mononuclear Fe active site and no iron-sulfur clusters, in contrast to the [FeFe] hydrogenases. [NiFe] and [FeFe] hydrogenases have some common features in their structures: Each enzyme has an active site and a few Fe-S clusters that are buried in protein. The active site, which is believed to be the place where catalysis takes place, is also a metallocluster, and each iron is coordinated by carbon monoxide (CO) and cyanide (CN−) ligands.[3]
https://en.wikipedia.org/wiki/Hydrogenase

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Insights into [FeFe]-Hydrogenase Structure, Mechanism, and Maturation

Hydrogenases are metalloenzymes that are key to energy metabolism in a variety of microbial communities. Divided into three classes based on their metal content, the [Fe]-, [FeFe]-, and [NiFe]-hydrogenases are evolutionarily unrelated but share similar nonprotein ligand assemblies at their active site metal centers that are not observed elsewhere in biology. These nonprotein ligands are critical in tuning enzyme reactivity, and their synthesis and incorporation into the active site clusters require a number of specific maturation enzymes. The wealth of structural information on different classes and different states of hydrogenase enzymes, biosynthetic intermediates, and maturation enzymes has contributed significantly to understanding the biochemistry of hydrogen metabolism. This review highlights the unique structural features of hydrogenases and emphasizes the recent biochemical and structural work that has created a clearer picture of the [FeFe]-hydrogenase maturation pathway.
https://www.sciencedirect.com/science/article/pii/S0969212611002152

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Development of an In Vitro Compartmentalization Screen for High-Throughput Directed Evolution of [FeFe] Hydrogenases James A. Stapleton,James R. Swartz , Published: December 6, 2010
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0015275

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Organization of Intracellular Reactions with Rationally Designed RNA Assemblies
Camille J. Delebecque1,2,3,4, Ariel B. Lindner3,4,*, Pamela A. Silver1,2,*, Faisal A. Aldaye1,2
Science  22 Jul 2011:  Vol. 333, Issue 6041, pp. 470-474  DOI: 10.1126/science.1206938
https://science.sciencemag.org/content/333/6041/470.abstract

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Front. Microbiol., 11 April 2014 | https://doi.org/10.3389/fmicb.2014.00142
Comparison of transcriptional profiles of Clostridium thermocellum grown on cellobiose and pretreated yellow poplar using RNA-Seq
Front. Microbiol., 11 April 2014 | https://doi.org/10.3389/fmicb.2014.00142
https://www.frontiersin.org/articles/10.3389/fmicb.2014.00142/full

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Maturation of cytosolic and nuclear iron–sulfur proteins
DJA Netz, J Mascarenhas, O Stehling, AJ Pierik… – Trends in cell …, 2014 – Elsevier
https://www.sciencedirect.com/science/article/abs/pii/S0962892413001967

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STRUCTURE, FUNCTION, AND FORMATION OF BIOLOGICAL IRON-SULFUR CLUSTERS
Annual Review of Biochemistry — Vol. 74:247-281 (Volume publication date 7 July 2005)
https://www.annualreviews.org/doi/abs/10.1146/annurev.biochem.74.082803.133518

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Recent Advances in Radical SAM Enzymology: New Structures and Mechanisms (2014)
Jiarui Wang, Rory P. Woldring, Gabriel D. Román-Meléndez, Alan M. McClain, Brian R. Alzua, and E. Neil G. Marsh*

Very recently, we have shown that empty α-carboxysome shells (about 100 nm in diameter) can be reconstructed by expressing the full set of shell proteins and can recruit mature O2-sensitive [FeFe]-hydrogenase and cofactors into the shell to create a novel hydrogen-producing as a novel nanoscale bioreactor, taking advantage of the O2-free (or O2-less) microenvironment created within the α-carboxysome shell (Li et al., 2020). The dimension and shape of the recombinant α-carboxysome shell are comparable to those of native carboxysomes, suggesting the improved enzyme loading and more close-to-native microenvironment compared with the shells with the reduced size.
https://pubs.acs.org/doi/abs/10.1021/cb5004674

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Chapter Five – RNA Study Using DNA Nanotechnology

Abstract:  Transcription is one of the fundamental steps of gene expression, where RNA polymerases (RNAPs) bind to their template genes and make RNAs. In addition to RNAP and the template gene, many molecules such as transcription factors are involved. The interaction and the effect of these factors depend on the geometry. Molecular layout of these factors, RNAP and gene is thus important. DNA nanotechnology is a promising technology that allows controlling of the molecular layout in the range of nanometer to micrometer scale with nanometer resolution; thus, it is expected to expand the RNA study beyond the current limit.
https://www.sciencedirect.com/science/article/pii/S1877117315002379

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Characterization of Hydrogen Metabolism in the Multicellular Green Alga Volvox carteri

” The genome of Volvox carteri contains two genes encoding putative [FeFe]-hydrogenases (HYDA1 and HYDA2), and the transcripts for these genes accumulate under anaerobic conditions.”
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0125324

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Development of an In Vitro Compartmentalization Screen for High-Throughput Directed Evolution of [FeFe]
Hydrogenases (2010)

Abstract 

Background: [FeFe] hydrogenase enzymes catalyze the formation and dissociation of molecular hydrogen with the help of a complex prosthetic group composed of common elements. The development of energy conversion technologies based on these renewable catalysts has been hindered by their extreme oxygen sensitivity. Attempts to improve the enzymes by directed evolution have failed for want of a screening platform capable of throughputs high enough to adequately sample heavily mutated DNA libraries. In vitro compartmentalization (IVC) is a powerful method capable of screening for multiple-turnover enzymatic activity at very high throughputs. Recent advances have allowed [FeFe] hydrogenases to be expressed and activated in the cell-free protein synthesis reactions on which IVC is based; however, IVC is a demanding technique with which many enzymes have proven incompatible.

Methodology/principal findings: Here we describe an extremely high-throughput IVC screen for oxygen-tolerant [FeFe] hydrogenases. We demonstrate that the [FeFe] hydrogenase CpI can be expressed and activated within emulsion droplets, and identify a fluorogenic substrate that links activity after oxygen exposure to the generation of a fluorescent signal. We present a screening protocol in which attachment of mutant genes and the proteins they encode to the surfaces of microbeads is followed by three separate emulsion steps for amplification, expression, and evaluation of hydrogenase mutants. We show that beads displaying active hydrogenase can be isolated by fluorescence-activated cell-sorting, and we use the method to enrich such beads from a mock library.

Conclusions/significance: [FeFe] hydrogenases are the most complex enzymes to be produced by cell-free protein synthesis, and the most challenging targets to which IVC has yet been applied. The technique described here is an enabling step towards the development of biocatalysts for a biological hydrogen economy.

https://pubmed.ncbi.nlm.nih.gov/21151915/

Full Article:(PDF)
https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.292.4946&rep=rep1&type=pdf

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Terms/Definitions

“Ferredoxins” (from Latin ferrum: iron + redox, often abbreviated “fd”) are iron–sulfur proteins that mediate electron transfer in a range of metabolic reactions. The term “ferredoxin” was coined by D.C. Wharton of the DuPont Co. and applied to the “iron protein” first purified in 1962 by Mortenson, Valentine, and Carnahan from the anaerobic bacterium Clostridium pasteurianum.  https://en.wikipedia.org/wiki/Ferredoxin

“Ligand” (Def) —  In coordination chemistry, a ligand[a] is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. –  https://en.wikipedia.org/wiki/Ligand

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