scholarly journals Synthetic Models for Nickel–Iron Hydrogenase Featuring Redox-Active Ligands

2017 ◽  
Vol 70 (5) ◽  
pp. 505 ◽  
Author(s):  
David Schilter ◽  
Danielle L. Gray ◽  
Amy L. Fuller ◽  
Thomas B. Rauchfuss
Keyword(s):  
Active Sites ◽  
Iron Sulfur Clusters ◽  
Nickel Iron Hydrogenase ◽  
Nickel Iron ◽  
Redox States ◽  
Iron Sulfur ◽  
Proton Relay ◽  
Redox Active ◽  
Iron Hydrogenase ◽  
Synthetic Models

The nickel–iron hydrogenase enzymes efficiently and reversibly interconvert protons, electrons, and dihydrogen. These redox proteins feature iron–sulfur clusters that relay electrons to and from their active sites. Reported here are synthetic models for nickel–iron hydrogenase featuring redox-active auxiliaries that mimic the iron–sulfur cofactors. The complexes prepared are NiII(μ-H)FeIIFeII species of formula [(diphosphine)Ni(dithiolate)(μ-H)Fe(CO)2(ferrocenylphosphine)]+ or NiIIFeIFeII complexes [(diphosphine)Ni(dithiolate)Fe(CO)2(ferrocenylphosphine)]+ (diphosphine = Ph2P(CH2)2PPh2 or Cy2P(CH2)2PCy2; dithiolate = –S(CH2)3S–; ferrocenylphosphine = diphenylphosphinoferrocene, diphenylphosphinomethyl(nonamethylferrocene) or 1,1′-bis(diphenylphosphino)ferrocene). The hydride species is a catalyst for hydrogen evolution, while the latter hydride-free complexes can exist in four redox states – a feature made possible by the incorporation of the ferrocenyl groups. Mixed-valent complexes of 1,1′-bis(diphenylphosphino)ferrocene have one of the phosphine groups unbound, with these species representing advanced structural models with both a redox-active moiety (the ferrocene group) and a potential proton relay (the free phosphine) proximal to a nickel–iron dithiolate.

scholarly journals Reduction of Technetium(VII) byDesulfovibrio fructosovorans Is Mediated by the Nickel-Iron Hydrogenase

2001 ◽  
Vol 67 (10) ◽  
pp. 4583-4587 ◽  
Author(s):  
Gilles De Luca ◽  
Pascale de Philip ◽  
Zorah Dermoun ◽  
Marc Rousset ◽  
André Verméglio
Keyword(s):  
Resting Cells ◽  
Nickel Iron Hydrogenase ◽  
Nickel Iron ◽  
Sulfate Reducing ◽  
Cell Extracts ◽  
Black Precipitate ◽  
Iron Hydrogenase ◽  
Reducing Activity ◽  
Reducing Bacteria

ABSTRACT Resting cells of the sulfate-reducing bacteriumDesulfovibrio fructosovorans grown in the absence of sulfate had a very high Tc(VII)-reducing activity, which led to the formation of an insoluble black precipitate. The involvement of a periplasmic hydrogenase in Tc(VII) reduction was indicated (i) by the requirement for hydrogen as an electron donor, (ii) by the tolerance of this activity to oxygen, and (iii) by the inhibition of this activity by Cu(II). Moreover, a mutant carrying a deletion in the nickel-iron hydrogenase operon showed a dramatic decrease in the rate of Tc(VII) reduction. The restoration of Tc(VII) reduction by complementation of this mutation with nickel-iron hydrogenase genes demonstrated the specific involvement of the periplasmic nickel-iron hydrogenase in the mechanism in vivo. The Tc(VII)-reducing activity was also observed with cell extracts in the presence of hydrogen. Under these conditions, Tc(VII) was reduced enzymatically to soluble Tc(V) or precipitated to an insoluble black precipitate, depending on the chemical nature of the buffer used. The purified nickel-iron hydrogenase performed Tc(VII) reduction and precipitation at high rates. These series of genetic and biochemical approaches demonstrated that the periplasmic nickel-iron hydrogenase of sulfate-reducing bacteria functions as a Tc(VII) reductase. The role of cytochromec 3 in the mechanism is also discussed.

scholarly journals Distinct Roles of the Salmonella enterica Serovar Typhimurium CyaY and YggX Proteins in the Biosynthesis and Repair of Iron-Sulfur Clusters

2014 ◽  
Vol 82 (4) ◽  
pp. 1390-1401 ◽  
Author(s):  
Jyoti Velayudhan ◽  
Joyce E. Karlinsey ◽  
Elaine R. Frawley ◽  
Lynne A. Becker ◽  
Margaret Nartea ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Salmonella Enterica ◽  
Active Sites ◽  
Nitrosative Stress ◽  
Iron Sulfur Cluster ◽  
Iron Sulfur Clusters ◽  
Content Type ◽  
Sulfur Cluster ◽  
Iron Sulfur ◽  
Serovar Typhimurium

ABSTRACTLabile [4Fe-4S]2+clusters found at the active sites of many dehydratases are susceptible to damage by univalent oxidants that convert the clusters to an inactive [3Fe-4S]1+form. Bacteria repair damaged clusters in a process that does not requirede novoprotein synthesis or the Isc and Suf cluster assembly pathways. The current study investigates the participation of the bacterial frataxin ortholog CyaY and the YggX protein, which are proposed to play roles in iron trafficking and iron-sulfur cluster repair. Previous reports found that individual mutations incyaYoryggXwere not associated with phenotypic changes inEscherichia coliandSalmonella entericaserovar Typhimurium, suggesting that CyaY and YggX might have functionally redundant roles. However, we have found that individual mutations incyaYoryggXconfer enhanced susceptibility to hydrogen peroxide inSalmonella entericaserovar Typhimurium. In addition, inactivation of thestm3944open reading frame, which is located immediately upstream ofcyaYand which encodes a putative inner membrane protein, dramatically enhances the hydrogen peroxide sensitivity of acyaYmutant. Overexpression of STM3944 reduces the elevated intracellular free iron levels observed in anS. Typhimuriumfurmutant and also reduces the total cellular iron content under conditions of iron overload, suggesting that thestm3944-encoded protein may mediate iron efflux. Mutations incyaYandyggXhave different effects on the activities of the iron-sulfur cluster-containing aconitase, serine deaminase, and NADH dehydrogenase I enzymes ofS. Typhimurium under basal conditions or following recovery from oxidative stress. In addition,cyaYandyggXmutations have additive effects on 6-phosphogluconate dehydratase-dependent growth during nitrosative stress, and acyaYmutation reducesSalmonellavirulence in mice. Collectively, these results indicate that CyaY and YggX play distinct supporting roles in iron-sulfur cluster biosynthesis and the repair of labile clusters damaged by univalent oxidants.Salmonellaexperiences oxidative and nitrosative stress within host phagocytes, and CyaY-dependent maintenance of labile iron-sulfur clusters appears to be important forSalmonellavirulence.

scholarly journals Protonation of Nickel–Iron Hydrogenase Models Proceeds after Isomerization at Nickel

2014 ◽  
Vol 136 (35) ◽  
pp. 12385-12395 ◽  
Author(s):  
Mioy T. Huynh ◽  
David Schilter ◽  
Sharon Hammes-Schiffer ◽  
Thomas B. Rauchfuss
Keyword(s):  
Nickel Iron Hydrogenase ◽  
Nickel Iron ◽  
Iron Hydrogenase

scholarly journals Steric and Electronic Effects of Ligand Substitution on Redox-Active Fe4S4-Based Coordination Polymers

2021 ◽  
Author(s):  
Omar Salinas ◽  
Jiaze Xie ◽  
Robert J. Papoular ◽  
Noah E. Horwitz ◽  
Erik Elkaim ◽  
...  
Keyword(s):  
Coordination Polymers ◽  
Photoelectron Spectroscopy ◽  
Electronic Effects ◽  
Iron Sulfur Clusters ◽  
Iron Sulfur ◽  
Redox Active ◽  
Metal Organic ◽  
Uv Visible ◽  
And Function ◽  
Fine Tune

<div>One of the notable advantages of molecular materials is the ability to precisely tune structure, properties, and function via molecular substitutions. While many studies have demonstrated this principle with classic carboxylate‐based coordination polymers, there are comparatively fewer examples where systematic changes to sulfur‐based coordination polymers have been investigated. Here we present such a study on 1D coordination chains of redox‐active</div><div>iron-sulfur clusters linked by methylated 1,4‐benzene‐dithiolates. A series of new iron-sulfur based coordination polymers were synthesized with either 2,5‐dimethyl‐1,4‐benzenedithiol (DMBDT) or 2,3,5,6‐tetramethyl‐1,4‐benzenedithiol. The structures of these compounds have been characterized based on synchrotron Xray</div><div>powder diffraction while their chemical and physical properties have been characterized by techniques including X‐ray photoelectron spectroscopy, cyclic voltammetry and UV–visible spectroscopy. Methylation results in the general trend of increasing electron‐richness in the series, but the tetramethyl version exhibits unexpected properties arising from steric constraints. All these results highlight how substitutions on organic linkers can modulate electronic factors to fine‐tune the electronic structures of metal‐organic materials.</div>

[5] Nickel-iron hydrogenase

1994 ◽  
pp. 43-68 ◽  
Author(s):  
Richard Cammack ◽  
Victor M. Fernandez ◽  
E. Claude Hatchikian
Keyword(s):  
Nickel Iron Hydrogenase ◽  
Nickel Iron ◽  
Iron Hydrogenase
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