scholarly journals Nickel-Sulfonate Mode of Substrate Binding for Forward and Reverse Reactions of Methyl-SCoM Reductase Suggest a Radical Mechanism Involving Long Range Electron Transfer

2021 ◽  
Author(s):  
Anjali Patwardhan ◽  
Ritimukta Sarangi ◽  
Bojana Ginovska ◽  
Simone Raugei ◽  
Stephen W. Ragsdale
Keyword(s):  
Electron Transfer ◽  
Hydrogen Atom ◽  
Long Range ◽  
Bound States ◽  
Thiol Group ◽  
Radical Mechanism ◽  
Anaerobic Oxidation Of Methane ◽  
Methyl Radical ◽  
Coenzyme M ◽  
Oxidation Of Methane

ABSTRACTMethyl-coenzyme M reductase (MCR) catalyzes both synthesis and anaerobic oxidation of methane (AOM). Its catalytic site contains Ni at the core of Cofactor F430. The Ni ion, in its low-valent Ni(I) state lights the fuse leading to homolysis of the C-S bond of methyl-coenzyme M (methyl-SCoM) to generate a methyl radical, which abstracts a hydrogen atom from Coenzyme B (HSCoB) to generate methane and the mixed disulfide CoMSSCoB. Direct reversal of this reaction activates methane to initiate anaerobic methane oxidation. Based on crystal structures, which reveal a Ni-thiol interaction between Ni(II)-MCR and inhibitor CoMSH, a Ni(I)-thioether complex with substrate methyl-SCoM has been transposed to canonical MCR mechanisms. Similarly, a Ni(I)-disulfide with CoMSSCoB is proposed for the reverse reaction. However, this Ni(I)-sulfur interaction poses a conundrum for the proposed hydrogen atom abstraction reaction because the >6 Å distance between the thiol group of SCoB and the thiol of SCoM observed in the structures appears too long for such a reaction. Spectroscopic, kinetic, structural and computational studies described here establish that both methyl-SCoM and CoMSSCoB bind to the active Ni(I) state of MCR through their sulfonate groups, forming a hexacoordinate Ni(I)-N/O complex, not Ni(I)-S. These studies rule out direct Ni(I)-sulfur interactions in both substrate-bound states. As a solution to the mechanistic conundrum, we propose that both forward and reverse MCR reactions emanate through long-range electron transfer from Ni(I)-sulfonate complexes with methyl-SCoM or CoMSSCoB, respectively.

Properties and reactivities of nonheme iron(iv)–oxo versus iron(v)–oxo: long-range electron transfer versus hydrogen atom abstraction

2014 ◽  
Vol 16 (41) ◽  
pp. 22611-22622 ◽  
Author(s):  
Baharan Karamzadeh ◽  
Devendra Singh ◽  
Wonwoo Nam ◽  
Devesh Kumar ◽  
Sam P. de Visser
Keyword(s):  
Electron Transfer ◽  
Hydrogen Atom ◽  
Long Range ◽  
Cation Radical ◽  
Nonheme Iron ◽  
Hydrogen Atom Abstraction ◽  
Computational Studies ◽  
Radical Species ◽  
Oxo Ligand

Computational studies show that the perceived nonheme iron(v)–oxo is actually an iron(iv)–oxo ligand cation radical species.

scholarly journals Comparative genomics reveals electron transfer and syntrophic mechanisms differentiating methanotrophic and methanogenic archaea

2021 ◽  
Author(s):  
Grayson L Chadwick ◽  
Connor T Skennerton ◽  
Rafael Laso-Perez ◽  
Andy O Leu ◽  
Daan R Speth ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Comparative Analysis ◽  
Comparative Genomics ◽  
Pure Culture ◽  
Methanogenic Archaea ◽  
Anaerobic Oxidation Of Methane ◽  
Genomic Features ◽  
Sulfate Reducing ◽  
Oxidation Of Methane ◽  
Reducing Bacteria

The anaerobic oxidation of methane coupled to sulfate reduction is a microbially mediated process requiring a syntrophic partnership between anaerobic methanotrophic (ANME) archaea and sulfate reducing bacteria (SRB). Based on genome taxonomy, ANME lineages are polyphyletic within the phylum Halobacterota, none of which have been isolated in pure culture. Here we reconstruct 28 ANME genomes from environmental metagenomes and flow sorted syntrophic consortia. Together with a reanalysis of previously published datasets, these genomes enable a comparative analysis of all marine ANME clades. We review the genomic features which separate ANME from their methanogenic relatives and identify what differentiates ANME clades. Large multiheme cytochromes and bioenergetic complexes predicted to be involved in novel electron bifurcation reactions are well-distributed and conserved in the ANME archaea, while significant variations in the anabolic C1 pathways exists between clades. Our analysis raises the possibility that methylotrophic methanogenesis may have evolved from a methanotrophic ancestor.

Long-range proton-coupled electron transfer in the Escherichia coli class Ia ribonucleotide reductase

2017 ◽  
Vol 61 (2) ◽  
pp. 281-292 ◽  
Author(s):  
Steven Y. Reece ◽  
Mohammad R. Seyedsayamdost
Keyword(s):  
Escherichia Coli ◽  
Electron Transfer ◽  
Amino Acid ◽  
Long Range ◽  
Ribonucleotide Reductase ◽  
Unnatural Amino Acids ◽  
Radical Mechanism ◽  
Tyrosyl Radical ◽  
Proton Coupled Electron Transfer ◽  
Vis Spectroscopy

Escherichia coli class Ia ribonucleotide reductase (RNR) catalyzes the conversion of nucleotides to 2′-deoxynucleotides using a radical mechanism. Each turnover requires radical transfer from an assembled diferric tyrosyl radical (Y•) cofactor to the enzyme active site over 35 Å away. This unprecedented reaction occurs via an amino acid radical hopping pathway spanning two protein subunits. To study the mechanism of radical transport in RNR, a suite of biochemical approaches have been developed, such as site-directed incorporation of unnatural amino acids with altered electronic properties and photochemical generation of radical intermediates. The resulting variant RNRs have been investigated using a variety of time-resolved physical techniques, including transient absorption and stopped-flow UV-Vis spectroscopy, as well as rapid freeze-quench EPR, ENDOR, and PELDOR spectroscopic methods. The data suggest that radical transport occurs via proton-coupled electron transfer (PCET) and that the protein structure has evolved to manage the proton and electron transfer co-ordinates in order to prevent ‘off-pathway’ reactivity and build-up of oxidised intermediates. Thus, precise design and control over the factors that govern PCET is key to enabling reversible and long-range charge transport by amino acid radicals in RNR.

scholarly journals Comparative genomics reveals electron transfer and syntrophic mechanisms differentiating methanotrophic and methanogenic archaea

PLoS Biology ◽  
2022 ◽  
Vol 20 (1) ◽  
pp. e3001508
Author(s):  
Grayson L. Chadwick ◽  
Connor T. Skennerton ◽  
Rafael Laso-Pérez ◽  
Andy O. Leu ◽  
Daan R. Speth ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Comparative Analysis ◽  
Comparative Genomics ◽  
Pure Culture ◽  
Methanogenic Archaea ◽  
Anaerobic Oxidation Of Methane ◽  
Genomic Features ◽  
Sulfate Reducing ◽  
Oxidation Of Methane ◽  
Reducing Bacteria

The anaerobic oxidation of methane coupled to sulfate reduction is a microbially mediated process requiring a syntrophic partnership between anaerobic methanotrophic (ANME) archaea and sulfate-reducing bacteria (SRB). Based on genome taxonomy, ANME lineages are polyphyletic within the phylum Halobacterota, none of which have been isolated in pure culture. Here, we reconstruct 28 ANME genomes from environmental metagenomes and flow sorted syntrophic consortia. Together with a reanalysis of previously published datasets, these genomes enable a comparative analysis of all marine ANME clades. We review the genomic features that separate ANME from their methanogenic relatives and identify what differentiates ANME clades. Large multiheme cytochromes and bioenergetic complexes predicted to be involved in novel electron bifurcation reactions are well distributed and conserved in the ANME archaea, while significant variations in the anabolic C1 pathways exists between clades. Our analysis raises the possibility that methylotrophic methanogenesis may have evolved from a methanotrophic ancestor.

scholarly journals Localization of Methyl-Coenzyme M Reductase as Metabolic Marker for Diverse Methanogenic Archaea

Archaea ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Christoph Wrede ◽  
Ulrike Walbaum ◽  
Andrea Ducki ◽  
Iris Heieren ◽  
Michael Hoppert
Keyword(s):  
Polyclonal Antibodies ◽  
Methanogenic Archaea ◽  
Growth Conditions ◽  
Laboratory Culture ◽  
Anaerobic Oxidation Of Methane ◽  
Coenzyme M ◽  
Microbial Biofilms ◽  
Oxidation Of Methane ◽  
Metabolic Marker ◽  
Methyl Coenzyme M Reductase

Methyl-Coenzyme M reductase (MCR) as key enzyme for methanogenesis as well as for anaerobic oxidation of methane represents an important metabolic marker for both processes in microbial biofilms. Here, the potential of MCR-specific polyclonal antibodies as metabolic marker in various methanogenic Archaea is shown. For standard growth conditions in laboratory culture, the cytoplasmic localization of the enzyme inMethanothermobacter marburgensis,Methanothermobacter wolfei,Methanococcus maripaludis,Methanosarcina mazei, and in anaerobically methane-oxidizing biofilms is demonstrated. Under growth limiting conditions on nickel-depleted media, at low linear growth of cultures, a fraction of 50–70% of the enzyme was localized close to the cytoplasmic membrane, which implies “facultative” membrane association of the enzyme. This feature may be also useful for assessment of growth-limiting conditions in microbial biofilms.

ON THE MATHEMATICAL MODELING OF SOLITON-MEDIATED LONG-RANGE ELECTRON TRANSFER

2010 ◽  
Vol 20 (01) ◽  
pp. 185-194 ◽  
Author(s):  
MANUEL G. VELARDE ◽  
ALEXANDER P. CHETVERIKOV ◽  
WERNER EBELING ◽  
DIRK HENNIG ◽  
JOHN J. KOZAK
Keyword(s):  
Mathematical Modeling ◽  
Electron Transfer ◽  
Long Range ◽  
Bound States ◽  
Supersonic Velocity ◽  
One Dimensional ◽  
Assisted Modes

We discuss here possible models for long-range electron transfer (ET) between a donor (D) and an acceptor (A) along an anharmonic (Morse–Toda) one-dimensional (1d)-lattice. First, it is shown that the electron may form bound states (solectrons) with externally, mechanically excited solitons in the lattice thus leading to one form of soliton-mediated transport. These solectrons generally move with supersonic velocity. Then, in a thermally excited lattice, it is shown that solitons can also trap electrons, forming similar solectron bound states; here, we find that ET based on hopping can be modeled as a diffusion-like process involving not just one but several solitons. It is shown that either of these two soliton-assisted modes of transport can facilitate ET over quite long distances.

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