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Showing 1 to 20 of 20 for “"Tyrosyl radical"”.
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Mechanism of biosynthesis of the dimanganese-tyrosyl radical cofactor of class lb Ribonucleotide reductase
… reduction, and p2 contains an essential stable tyrosyl radical (Y·), generated by oxidation of a dinuclear metal cluster. The diferric-Y (Fe" 2-Y·) cofactor of the class Ia RNRs self-assembles by reaction of Fe"2-NrdB with 02 and a reducing equivalent. Whether the class Ib RNRs utilize a diiron …
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Mechanism of assembly of the tyrosyl radical-diiron(III) cofactor of E. coli ribonucleotide reductase
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1996.
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On the chemical mechanism of assembly of the tyrosyl radical-dinulcear iron cluster cofactor of E. coli ribonucleotide reductase
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1993.
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Photochemical ribonucleotide reductase for the study of proton-coupled electron transfer
… catalysis in enzymes often rely on amino acid radicals as intermediates. The generation and transport of these radicals are synonymous with proton-coupled electron transfer (PCET), which intrinsically is a quantum mechanical effect as both the electron and proton tunnel. The caveat to PCET is …
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Biochemical characterization of a-type heme-copper oxidases in escherichia coli, bacillus subtilis and thermus thermophilus
… and Gln101) involved in ubiquinone semiquinone radical stabilization at quinone binding site in E. coli cytochrome bo3 oxidase. Similar result was reported on cytochrome aa3-600 oxidase in B. subtilis, a close homolog to cytochrome bo3 that uses menaquinone instead of ubiquinone. Recently, in …
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Mechanistic studies of the Class I ribonucleotide reductase from Escherichia coli
… reduction occurs, and R2 contains the diferric-tyrosyl radical (Y · ) cofactor essential for radical initiation on R1. The rate-determining step in E. coli RNR has recently been shown to be a physical step prior to generation of the putative thiyl radical (S · ) on C439. Thus, the chemistry of …
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Influence of the reducing agent triphenylphosphine on cyclooxygenase-1 metabolism of arachidonic acid
… influenced by lipid hydroperoxides. The tyrosyl radical that abstracts the 13 pro(s) hydrogen from AA to initiate the COX catalytic cycle is generated by iron-oxo derivatives in the enzyme that result from lipid hydroperoxide interaction with heme iron. Commercial preparations of …
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Biochemical Studies on the Catalytic Cycle of Cytochrome C Oxidase in Rhodobacter Sphaeroides
… between Y288 and H284 and the formation of a tyrosyl radical species in the catalytic cycle of cytochrome c oxidase.
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Structural investigations of class la ribonucleotide reductases by electron microscopy
… reduction. Chemistry is initiated by a thiyl-radical (C439·) in the active site of [beta]2 that is reversibly generated by a diferric-tyrosyl radical cofactor (Y122·) in [beta]2 by a series of proton-coupled electron transfer steps: Y122[beta] <-> [W48[beta]] <-> Y356[beta] <-> Y731[alpha] - …
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Proton-coupled electron transfer in the Escherichia coli ribonucleotide reductase
… their corresponding deoxynucleotides via a thiyl radical hydrogen abstraction mechanism. As this is the only cellular pathway for production of the monomeric precursors required for DNA synthesis, the regulation of RNR is crucial to controlling the cell cycle by the availability of substrate pools …
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Investigation of the mechanism of radical propagation in E. coli ribonucleotide reductase by site-specific incorporation of unnatural amino acids
… of nucleotide reduction and 02 contains a diiron tyrosyl radical (Y122*) cofactor. Each turnover requires radical propagation from the Y122* in 32 to the active site of a2 over 35 A. The mechanism of this unprecedented, long-range radical propagation step is poorly understood. Based on structural …
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Defining the active form of ribonucleotide reductase from Saccharomyces cerevisiae in vitro and in vivo
… small subunit (R2) which houses the diferric tyrosyl radical (Y.) cofactor required for RNR activity. S. cerevisiae has two Rl-like proteins, Y1 and Y3 and two R2-like proteins, Y2 and Y4. In vitro studies have focused on defining the active form of the R2 subunit. As isolated, Y2 and Y4 are …
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Metalloprotein engineering with unnatural amino acids: application in functional heme-copper oxidase and azurin
… the widely proposed mechanism that involves a tyrosyl radical, its direct observation under O2 reduction condition remains elusive. Using a functional oxidase model in myoglobin called F33Y-CuBMb, we observed of radical under H2O2 reaction condition by electron paramagnetic resonance (EPR) …
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Discovery and investigation of the novel overall activity allosteric regulation of the Bacillus subtilis class Ib ribonucleotide reductase
… p houses a catalytically essential dimanganic-tyrosyl radical (Mn(III)2-Y*). The allosteric regulation of lb RNR activity has only been studied with the Salmonella enterica enzyme, which exhibits substrate specificity allosteric regulation by ATP and 2'-deoxynucleoside 5'-triphosphates (dNTPs), …
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Mechanistic studies of proton-coupled electron transfer in aminotyrosine- and fluorotyrosine- substituted class Ia Ribonucleotide reductase
… electron transfer (PCET) to propagate a stable tyrosyl radical (Yi22-) in P2 over a distance of >35 A to an active site cysteine (C4 3 9) in a2 on each turnover. Generation of the cysteinyl radical (C4 3 9-) initiates active site nucleotide reduction. Radical propagation over 35 A by a pure …
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Photoinitiated proton-coupled electron transfer and radical transport kinetics in class la ribonucleotide reductase
… in biology, underpinning key processes such as radical transport, energy transduction, and enzymatic substrate activation. Ribonucleotide reductases (RNRs) rely on PCET to mediate the rate-limiting step in the synthesis of DNA precursors. E. coli class Ia RNR consists of two dimeric subunits: …
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Structural studies of allosteric regulation in the class Ia Ribonucleotide reductase from Escherichia coli
… Ia enzyme requires two subunits to catalyze the radical-based reduction reaction. [beta]2 houses a diferric-tyrosyl radical cofactor and [alpha]2 contains the active site and two allosteric effector binding sites. Allosteric control of RNR fine-tunes both the relative ratios (via substrate …
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In vivo cofactor biosynthesis and maintenance in the class Ia ribonucleotide reductase small subunit of Escherichia coli
… reductases (RNRs) contains a diferric tyrosyl radical (Y*) cofactor essential for the conversion of nucleotides to deoxynucleotides that are needed for DNA synthesis and repair. The mechanism and factors involved in the biosynthesis, maintenance and regulation of this cluster remains …
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Mechanistic studies of the radical transport pathway in aminotyrosine-substituted class Ia ribonucleotide reductase
… The [beta]2 subunit harbors the stable diferric-tyrosyl radical cofactor (Y 122*) that reversibly oxidizes the active site cysteine (C₄₃₉) in [alpha]2. This oxidation requires a long-range radical transport (RT) pathway consisting of proton-coupled electron transfer (PCET) events through …
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Mechanistic investigations of the radical transport pathway in fluorotyrosine-substituted class Ia ribonucleotide reductases
… [alpha]2[beta]2 complex. A stable diferric-tyrosyl radical (Y₁₂₂*) in [beta]2 reversibly oxidizes an active site cysteine (C₄₃₉*) in [alpha]2 via multiple proton-coupled electron transfer (PCET) steps through conserved aromatic amino acid residues: Y₁₂₂* <-> [W₄₈] <-> Y₃₅₆ in [beta]2 to Y₇₃₁ …