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Full-Text Articles in Physics
Reversible Dissociation Of Thiolate Ligands From Molybdenum In An Enzyme Of The Dimethyl Sulfoxide Reductase Family, Robert C. Bray, Benjamin Adams, Andrew T. Smith, Brian Bennett, Susan Bailey
Reversible Dissociation Of Thiolate Ligands From Molybdenum In An Enzyme Of The Dimethyl Sulfoxide Reductase Family, Robert C. Bray, Benjamin Adams, Andrew T. Smith, Brian Bennett, Susan Bailey
Physics Faculty Research and Publications
Much is unknown concerning the role of thiolate ligands of molybdenum in molybdopterin enzymes. It has been suggested that thiolate dissociation from molybdenum is part of the catalytic mechanism of bis-molybdopterin enzymes of the dimethyl sulfoxide reductase (DMSOR) family. For DMSOR from Rhodobacter capsulatus, thiolate dissociation has therefore been investigated crystallographically, by UV/visible spectroscopy, and by enzyme assays. When crystallized from sodium citrate, all four thiolates of DMSOR are within bonding distance of Mo, but after extended exposure to Na+-Hepes, a pair of thiolates dissociates, a mixture of structures being indicated after shorter exposures to this buffer. …
Dimethylsulfoxide Reductase: An Enzyme Capable Of Catalysis With Either Molybdenum Or Tungsten At The Active Site, Lisa J. Stewart, Susan Bailey, Brian Bennett, John M. Charnock, C. David Garner, Alan S. Mcalpine
Dimethylsulfoxide Reductase: An Enzyme Capable Of Catalysis With Either Molybdenum Or Tungsten At The Active Site, Lisa J. Stewart, Susan Bailey, Brian Bennett, John M. Charnock, C. David Garner, Alan S. Mcalpine
Physics Faculty Research and Publications
DMSO reductase (DMSOR) from Rhodobacter capsulatus, well-characterised as a molybdoenzyme, will bind tungsten. Protein crystallography has shown that tungsten in W-DMSOR is ligated by the dithiolene group of the two pyranopterins, the oxygen atom of Ser147 plus another oxygen atom, and is located in a very similar site to that of molybdenum in Mo-DMSOR. These conclusions are consistent with W LIII-edge X-ray absorption, EPR and UV/visible spectroscopic data. W-DMSOR is significantly more active than Mo-DMSOR in catalysing the reduction of DMSO but, in contrast to the latter, shows no significant ability to catalyse the oxidation of DMS.
Reversible Carbon Monoxide Binding And Inhibition At The Active Site Of The Fe-Only Hydrogenase, Brian Bennett, Brian J. Lemon, John W. Peters
Reversible Carbon Monoxide Binding And Inhibition At The Active Site Of The Fe-Only Hydrogenase, Brian Bennett, Brian J. Lemon, John W. Peters
Physics Faculty Research and Publications
Carbon monoxide binding and inhibition have been investigated by electron paramagnetic resonance (EPR) spectroscopy in solution and in crystals of structurally described states of the Fe-only hydrogenase (CpI) from Clostridium pasteurianum. Simulation of the EPR spectrum of the as-isolated state indicates that the main component of the EPR spectrum consists of the oxidized state of the “H cluster” and components due to reduced accessory FeS clusters. Addition of carbon monoxide to CpI in the presence of dithionite results in the inhibition of hydrogen evolution activity, and a characteristic axial EPR signal [geff(1), geff(2), and …
Sulfite: Cytochrome C Oxidoreductase From Thiobacillus Novellus, Ulrike Kappler, Brian Bennett, Jörg Rethmeier, Günter Schwarz, Rainer Deutzmann, Alistair G. Mcewan, Christiane Dahl
Sulfite: Cytochrome C Oxidoreductase From Thiobacillus Novellus, Ulrike Kappler, Brian Bennett, Jörg Rethmeier, Günter Schwarz, Rainer Deutzmann, Alistair G. Mcewan, Christiane Dahl
Physics Faculty Research and Publications
Direct oxidation of sulfite to sulfate occurs in various photo- and chemotrophic sulfur oxidizing microorganisms as the final step in the oxidation of reduced sulfur compounds and is catalyzed by sulfite: cytochrome c oxidoreductase (EC1.8.2.1). Here we show that the enzyme from Thiobacillus novellus is a periplasmically located αβ heterodimer, consisting of a 40.6-kDa subunit containing a molybdenum cofactor and an 8.8-kDa mono-heme cytochrome c 552 subunit (midpoint redox potential, E m8.0 = +280 mV). The organic component of the molybdenum cofactor was identified as molybdopterin contained in a 1:1 ratio to the Mo content of the enzyme. Electron …
Divalent Metal Binding Properties Of The Methionyl Aminopeptidase From Escherichia Coli, Ventris M. D'Souza, Brian Bennett, Alicja J. Copik, Richard C. Holz
Divalent Metal Binding Properties Of The Methionyl Aminopeptidase From Escherichia Coli, Ventris M. D'Souza, Brian Bennett, Alicja J. Copik, Richard C. Holz
Physics Faculty Research and Publications
The metal-binding properties of the methionyl aminopeptidase from Escherichia coli (MetAP) were investigated. Measurements of catalytic activity as a function of added Co(II) and Fe(II) revealed that maximal enzymatic activity is observed after the addition of only 1 equiv of divalent metal ion. Based on these studies, metal binding constants for the first metal binding event were found to be 0.3 ± 0.2 μM and 0.2 ± 0.2 μM for Co(II)- and Fe(II)-substituted MetAP, respectively. Binding of excess metal ions (>50 equiv) resulted in the loss of ∼50% of the catalytic activity. Electronic absorption spectral titration of a 1 …
Inhibition Of The Aminopeptidase From Aeromonas Proteolytica By L-Leucinethiol: Kinetic And Spectroscopic Characterization Of A Slow, Tight-Binding Inhibitor–Enzyme Complex, David L. Bienvenue, Brian Bennett, Richard C. Holz
Inhibition Of The Aminopeptidase From Aeromonas Proteolytica By L-Leucinethiol: Kinetic And Spectroscopic Characterization Of A Slow, Tight-Binding Inhibitor–Enzyme Complex, David L. Bienvenue, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
The peptide inhibitor l-leucinethiol (LeuSH) was found to be a potent, slow-binding inhibitor of the aminopeptidase from Aeromonas proteolytica (AAP). The overall potency (KI*) of LeuSH was 7 nM while the corresponding alcohol l-leucinol (LeuOH) was a simple competitive inhibitor of much lower potency (KI=17 μM). These data suggest that the free thiol is likely involved in the formation of the E·I and E·I* complexes, presumably providing a metal ligand. In order to probe the nature of the interaction of LeuSH and LeuOH with the dinuclear active site of AAP, we have …