Corrigendum to "Transport limited adsorption experiments give a new lower estimate of the turnover frequency of hydrogenase 1" BBA Advances 3 (2023) 100090.

[This corrects the article DOI: 10.1016/j.bbadva.

A Chimeric NiFe Hydrogenase Heterodimer to Assess the Role of the Electron Transfer Chain in Tuning the Enzyme's Catalytic Bias and Oxygen Tolerance.

The observation that some homologous enzymes have the same active site but very different catalytic properties demonstrates the importance of long-range effects in enzyme catalysis, but these effects are often difficult to rationalize. The NiFe hydrogenases 1 and 2 (Hyd 1 and Hyd 2) from both consist of a large catalytic subunit that embeds the same dinuclear active site and a small electron-transfer subunit with a chain of three FeS clusters. Hyd 1 is mostly active in H oxidation and resistant to inhibitors, whereas Hyd 2 also catalyzes H production and is strongly inhibited by O and CO.

Transport limited adsorption experiments give a new lower estimate of the turnover frequency of hydrogenase 1.

Protein Film Electrochemistry is a technique in which a redox enzyme is directly wired to an electrode, which substitutes for the natural redox partner. In this technique, the electrical current flowing through the electrode is proportional to the catalytic activity of the enzyme. However, in most cases, the amount of enzyme molecules contributing to the current is unknown and the absolute turnover frequency cannot be determined.

An essential role of the reversible electron-bifurcating hydrogenase Hnd for ethanol oxidation in .

The tetrameric cytoplasmic FeFe hydrogenase Hnd from (formely ) catalyses H oxidation and couples the exergonic reduction of NAD to the endergonic reduction of a ferredoxin by using a flavin-based electron-bifurcating mechanism. Regarding its implication in the bacterial physiology, we previously showed that Hnd, which is non-essential when bacteria grow fermentatively on pyruvate, is involved in ethanol metabolism. Under these conditions, it consumes H to produce reducing equivalents for ethanol production as a fermentative product.

Carbon Fixation in the Chemolithoautotrophic Bacterium Involves Two Low-Potential Ferredoxins as Partners of the PFOR and OGOR Enzymes.

is a microaerophilic hydrogen- and sulfur -oxidizing bacterium that assimilates CO via the reverse tricarboxylic acid cycle (rTCA). Key enzymes of this pathway are pyruvate:ferredoxin oxidoreductase (PFOR) and 2-oxoglutarate:ferredoxin oxidoreductase (OGOR), which are responsible, respectively, for the reductive carboxylation of acetyl-CoA to pyruvate and of succinyl-CoA to 2-oxoglutarate, two energetically unfavorable reactions that require a strong reduction potential. We have confirmed, by biochemistry and proteomics, that possesses a pentameric version of these enzyme complexes ((αβγδε)) and that they are highly abundant in the cell.

NMR-based metabolomic analysis of the physiological role of the electron-bifurcating FeFe-hydrogenase Hnd in Solidesulfovibrio fructosivorans under pyruvate fermentation.

Solidesulfovibrio fructosivorans (formely Desulfovibrio fructosovorans), an anaerobic sulfate-reducing bacterium, possesses six gene clusters encoding six hydrogenases catalyzing the reversible oxidation of hydrogen gas (H) into protons and electrons. One of these, named Hnd, was demonstrated to be an electron-bifurcating hydrogenase Hnd (Kpebe et al., 2018).

The electron-bifurcating FeFe-hydrogenase Hnd is involved in ethanol metabolism in Desulfovibrio fructosovorans grown on pyruvate.

Desulfovibrio fructosovorans, a sulfate-reducing bacterium, possesses six gene clusters encoding six hydrogenases catalyzing the reversible oxidation of H into protons and electrons. Among them, Hnd is an electron-bifurcating hydrogenase, coupling the exergonic reduction of NAD to the endergonic reduction of a ferredoxin with electrons derived from H . It was previously hypothesized that its biological function involves the production of NADPH necessary for biosynthetic purposes.

Electrochemical Characterization of a Complex FeFe Hydrogenase, the Electron-Bifurcating Hnd From .

Hnd, an FeFe hydrogenase from , is a tetrameric enzyme that can perform flavin-based electron bifurcation. It couples the oxidation of H to both the exergonic reduction of NAD and the endergonic reduction of a ferredoxin. We previously showed that Hnd retains activity even when purified aerobically unlike other electron-bifurcating hydrogenases.

Hydrogenases and H metabolism in sulfate-reducing bacteria of the Desulfovibrio genus.

Hydrogen metabolism plays a central role in sulfate-reducing bacteria of the Desulfovibrio genus and is based on hydrogenases that catalyze the reversible conversion of protons into dihydrogen. These metabolically versatile microorganisms possess a complex hydrogenase system composed of several enzymes of both [FeFe]- and [NiFe]-type that can vary considerably from one Desulfovibrio species to another. This review covers the molecular and physiological aspects of hydrogenases and H metabolism in Desulfovibrio but focuses particularly on our model bacterium Desulfovibrio fructosovorans.

A new mechanistic model for an O-protected electron-bifurcating hydrogenase, Hnd from Desulfovibrio fructosovorans.

The genome of the sulfate-reducing and anaerobic bacterium Desulfovibrio fructosovorans encodes different hydrogenases. Among them is Hnd, a tetrameric cytoplasmic [FeFe] hydrogenase that has previously been described as an NADP-specific enzyme (Malki et al., 1995).

Phototrophic hydrogen production from a clostridial [FeFe] hydrogenase expressed in the heterocysts of the cyanobacterium Nostoc PCC 7120.

The conversion of solar energy into hydrogen represents a highly attractive strategy for the production of renewable energies. Photosynthetic microorganisms have the ability to produce H from sunlight but several obstacles must be overcome before obtaining a sustainable and efficient H production system. Cyanobacteria harbor [NiFe] hydrogenases required for the consumption of H.

Expression of terminal oxidases under nutrient-starved conditions in Shewanella oneidensis: detection of the A-type cytochrome c oxidase.

Shewanella species are facultative anaerobic bacteria that colonize redox-stratified habitats where O2 and nutrient concentrations fluctuate. The model species Shewanella oneidensis MR-1 possesses genes coding for three terminal oxidases that can perform O2 respiration: a bd-type quinol oxidase and cytochrome c oxidases of the cbb3-type and the A-type. Whereas the bd- and cbb3-type oxidases are routinely detected, evidence for the expression of the A-type enzyme has so far been lacking.

A biochemical approach to study the role of the terminal oxidases in aerobic respiration in Shewanella oneidensis MR-1.

The genome of the facultative anaerobic γ-proteobacterium Shewanella oneidensis MR-1 encodes for three terminal oxidases: a bd-type quinol oxidase and two heme-copper oxidases, a A-type cytochrome c oxidase and a cbb 3-type oxidase. In this study, we used a biochemical approach and directly measured oxidase activities coupled to mass-spectrometry analysis to investigate the physiological role of the three terminal oxidases under aerobic and microaerobic conditions. Our data revealed that the cbb 3-type oxidase is the major terminal oxidase under aerobic conditions while both cbb 3-type and bd-type oxidases are involved in respiration at low-O2 tensions.

H₂-dependent azoreduction by Shewanella oneidensis MR-1: involvement of secreted flavins and both [Ni-Fe] and [Fe-Fe] hydrogenases.

In this paper, the hydrogen (H2)-dependent discoloration of azo dye amaranth by Shewanella oneidensis MR-1 was investigated. Experiments with hydrogenase-deficient strains demonstrated that periplasmic [Ni-Fe] hydrogenase (HyaB) and periplasmic [Fe-Fe] hydrogenase (HydA) are both respiratory hydrogenases of dissimilatory azoreduction in S. oneidensis MR-1.

Drosophila translational elongation factor-1gamma is modified in response to DOA kinase activity and is essential for cellular viability.

Drosophila translational elongation factor-1gamma (EF1gamma) interacts in the yeast two-hybrid system with DOA, the LAMMER protein kinase of Drosophila. Analysis of mutant EF1gamma alleles reveals that the locus encodes a structurally conserved protein essential for both organismal and cellular survival. Although no genetic interactions were detected in combinations with mutations in EF1alpha, an EF1gamma allele enhanced mutant phenotypes of Doa alleles.

Dissection of darkener of apricot kinase isoform functions in Drosophila.

The Darkener of apricot (Doa) locus of Drosophila encodes a LAMMER protein kinase affecting alterative splicing, and hence sex determination, via the phosphorylation of SR and SR-like proteins. Doa encodes 6 different kinases via alternative promoter usage. To provide further insight into the roles of the multiple isoforms, we mapped polymorphisms, deletions, and P-element insertions in the locus, identifying several that are largely, if not completely, isoform specific in their effects.

Alternative promoter usage generates multiple evolutionarily conserved isoforms of Drosophila DOA kinase.

The unique LAMMER (or Clk) protein kinase of Drosophila is encoded at the Doa locus. To better understand the pleiotropic effects of Doa mutations, we describe the structure and expression of the multiple RNA and protein products of the locus, as well as their evolutionary conservation among Drosophila. The gene produces at least six different protein isoforms, primarily through alternative promoter usage, generating kinases with virtually identical catalytic domains but variable N-terminal noncatalytic domains.

Polymorphisms in the C-terminal domain of MECP2 in mentally handicapped boys: implications for genetic counselling.

Numerous recent reports have proposed that mutations in the C-terminal domain of the MECP2 gene could be a frequent cause of mental retardation in males. We have identified two mutations in this particular domain (S359P and E397K) in two boys who were screened for MECP2 mutations in a series of 23 mentally handicapped boys fitting the clinical description of the previously reported cases. A detailed familial study based on three generations shows that the first mutation (S359P) was also inherited by a healthy cousin thus ruling out its involvement in the etiology of the phenotype of this patient.