Bioenergetic aspects of archaeal and bacterial hydrogen metabolism

Pinske, Constanze

doi:10.1016/bs.ampbs.2019.02.005

Cited by 14 publications

(9 citation statements)

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“…14,15 The E. coli FHL-1 complex, composed of the membrane-bound [NiFe]-H 2 ase 3 (HYD-3/HycE) and FDH-H (FdhF; Figure 1a), represents a well-studied FHL, evolving H 2 under fermentative conditions. 11,12 The constituent enzymatic units of FHL-1 have been demonstrated to be reversible electrocatalysts, 16−20 but the complex is catalytically biased toward H 2 production from formate. 14,15,19 Interconversion of HCO 2 – /H 2 has also been reported in whole-cell studies, 14,20 notably in sulfate-reducing bacteria in the absence of sulfate.…”

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“…FHL complexes are biological machines for HCO 2 – /H 2 interconversion . They are either membrane-associated complexes composed of a multisubunit [NiFe]-H 2 ase coupled to an FDH, − or smaller soluble complexes of an [FeFe]-H 2 ase and an FDH. , The E. coli FHL-1 complex, composed of the membrane-bound [NiFe]-H 2 ase 3 (HYD-3/HycE) and FDH-H (FdhF; Figure a), represents a well-studied FHL, evolving H 2 under fermentative conditions. , The constituent enzymatic units of FHL-1 have been demonstrated to be reversible electrocatalysts, − but the complex is catalytically biased toward H 2 production from formate. ,, Interconversion of HCO 2 – /H 2 has also been reported in whole-cell studies, , notably in sulfate-reducing bacteria in the absence of sulfate. , Desulfovibrio vulgaris Hildenborough can grow by converting formate to H 2 , with formate oxidation catalyzed by a periplasmic FDH, and H 2 produced either via direct (periplasmic H 2 ase) or transmembrane electron transfer (cytoplasmic H 2 ase) …”

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Reversible and Selective Interconversion of Hydrogen and Carbon Dioxide into Formate by a Semiartificial Formate Hydrogenlyase Mimic

et al. 2019

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The biological formate hydrogenlyase (FHL) complex links a formate dehydrogenase (FDH) to a hydrogenase (H2ase) and produces H2 and CO2 from formate via mixed-acid fermentation in Escherichia coli. Here, we describe an electrochemical and a colloidal semiartificial FHL system that consists of an FDH and a H2ase immobilized on conductive indium tin oxide (ITO) as an electron relay. These in vitro systems benefit from the efficient wiring of a highly active enzyme pair and allow for the reversible conversion of formate to H2 and CO2 under ambient temperature and pressure. The hybrid systems provide a template for the design of synthetic catalysts and surpass the FHL complex in vivo by storing and releasing H2 on demand by interconverting CO2/H2 and formate with minimal bias in either direction.

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Reversible and Selective Interconversion of Hydrogen and Carbon Dioxide into Formate by a Semiartificial Formate Hydrogenlyase Mimic

et al. 2019

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“…Hydrogenases (Hyd) 1 and 2 of Escherichia coli are membrane‐associated H 2 ‐oxidizing enzymes that face the periplasmic side of the membrane . Hyd‐1 represents one half of a classical redox‐loop with two heme groups in the membrane subunit, which transfer electrons against the membrane potential towards the cytoplasmic side for quinone reduction and concomitant uptake of protons . Hyd‐2 also couples H 2 ‐oxidation to quinone reduction, but the membrane anchor subunit HybB has no cofactor .…”

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Amino acid variants of the HybB membrane subunit of Escherichia coli [NiFe]‐hydrogenase‐2 support a role in proton transfer

2019

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[NiFe]‐hydrogenase (Hyd) 2 of Escherichia coli has been proposed to generate proton motive force during H2‐oxidation, which it is dependent on if cells are incubated anaerobically with glycerol to drive reverse H2‐production. The integral membrane subunit HybB is required for proton transfer (PT) by Hyd‐2 but has no cofactor. To provide evidence for PT by HybB, we analyzed the roles of conserved amino acid residues in a predicted proton channel. Exchange of conserved residues identified residues Y99, E133, H184, and E228 as mandatory for PT from the cytoplasm and quinol oxidation. In contrast, exchange of W54, D58, or R89 rendered Hyd‐2 uni‐directional and influenced the equilibrium. Our findings show that HybB is the key subunit in PT.

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“…Instead, the architecture of the OHR complex, featuring the NrfD-type MAP represented by the OmeB subunit, suggests pmf generation through direct proton translocation across the membrane. However, the exact mechanism – whether proton pumping ( Duarte et al, 2021 ), vectorial proton transport onto the halogenated substrate ( Pinske, 2019 ), or a combination thereof ( Figure 1D ) – remains unclear.…”

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Dehalococcoides mccartyi strain CBDB1 takes up protons from the cytoplasm to reductively dehalogenate organohalides indicating a new modus of proton motive force generation

Hellmold,

Eberwein,

Phan

et al. 2023

Front. Microbiol.

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Proton translocation across the cytoplasmic membrane is a vital process for all organisms. Dehalococcoides strains are strictly anaerobic organohalide respiring bacteria that lack quinones and cytochromes but express a large membrane-bound protein complex (OHR complex) proposed to generate a proton gradient. However, its functioning is unclear. By using a dehalogenase-based enzyme activity assay with deuterium-labelled water in various experimental designs, we obtained evidence that the halogen atom of the halogenated electron acceptor is substituted with a proton from the cytoplasm. This suggests that the protein complex couples exergonic electron flux through the periplasmic subunits of the OHR complex to the endergonic transport of protons from the cytoplasm across the cytoplasmic membrane against the proton gradient to the halogenated electron acceptor. Using computational tools, we located two proton-conducting half-channels in the AlphaFold2-predicted structure of the OmeB subunit of the OHR complex, converging in a highly conserved arginine residue that could play a proton gatekeeper role. The cytoplasmic proton half-channel in OmeB is connected to a putative proton-conducting path within the reductive dehalogenase subunit. Our results indicate that the reductive dehalogenase and its halogenated substrate serve as both electron and proton acceptors, providing insights into the proton translocation mechanism within the OHR complex and contributing to a better understanding of energy conservation in D. mccartyi strains. Our results reveal a very simple mode of energy conservation in anaerobic bacteria, showing that proton translocation coupled to periplasmic electron flow might have importance also in other microbial processes and biotechnological applications.

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Bioenergetic aspects of archaeal and bacterial hydrogen metabolism

Cited by 14 publications

References 114 publications

Reversible and Selective Interconversion of Hydrogen and Carbon Dioxide into Formate by a Semiartificial Formate Hydrogenlyase Mimic

Reversible and Selective Interconversion of Hydrogen and Carbon Dioxide into Formate by a Semiartificial Formate Hydrogenlyase Mimic

Amino acid variants of the HybB membrane subunit of Escherichia coli [NiFe]‐hydrogenase‐2 support a role in proton transfer

Dehalococcoides mccartyi strain CBDB1 takes up protons from the cytoplasm to reductively dehalogenate organohalides indicating a new modus of proton motive force generation

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