Peter E. Doan

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Oxidative stress leads to the up-regulation of many antioxidant enzymes including Cu,Zn superoxide dismutase (SOD1) via transcriptional mechanisms; however, few examples of posttranslational regulation are known. The copper chaperone for SOD1 (CCS) is involved in physiological SOD1 activation, and its primary function is thought to be delivery of copper to(More)
The plasmid-encoded pco copper resistance operon in Escherichia coli consists of seven genes that are expressed from two pco promoters in response to elevated copper; however, little is known about how they mediate resistance to excess environmental copper. Two of the genes encode the soluble periplasmic proteins PcoA and PcoC. We show here that(More)
Despite the current availability of several crystal structures of purple acid phosphatases, to date there is no direct evidence for solvent-derived ligands occupying terminal positions in the active enzyme. This is of central importance, because catalysis has been shown to proceed through the direct attack on a metal-bound phosphate ester by a(More)
Continuous wave electron nuclear double resonance (CW ENDOR) spectra of [delta-15N,epsilon(-14)N]histidine-labeled phthalate dioxygenase (PDO) from Pseudomonas cepacia were recorded and found to be virtually identical to those previously recorded from [delta,epsilon-15N2]histidine-labeled protein [Gurbiel, R. J., Batie, C. J., Sivaraja, M., True, A. E.,(More)
Nitrogenase is the metalloenzyme that catalyzes the nucleotide-dependent reduction of N(2), as well as reduction of a variety of other triply bonded substrates, including the alkyne, acetylene. Substitution of the alpha-70(Val) residue in the nitrogenase MoFe protein by alanine expands the range of substrates to include short-chain alkynes not reduced by(More)
Particulate methane monooxygenase (pMMO) is a membrane-bound enzyme that catalyzes the oxidation of methane to methanol in methanotropic bacteria. Understanding how this enzyme hydroxylates methane at ambient temperature and pressure is of fundamental chemical and potential commercial importance. Difficulties in solubilizing and purifying active pMMO have(More)
We previously used a combination of continuous-wave (CW) and pulsed electron-nuclear double resonance (ENDOR) protocols to identify the types of protonated oxygen (OH(x)) species and their disposition within the Fe(III)/Fe(IV) cluster of intermediate X, the direct precursor of the essential diferric-tyrosyl radical cofactor of the beta2 subunit of(More)
A large variety of functional self-assembled supramolecular nanostructures have been reported over recent decades. The experimental approach to these systems initially focused on the design of molecules with specific interactions that lead to discrete geometric structures, and more recently on the kinetics and mechanistic pathways of self-assembly. However,(More)
Activation of the diferrous center of the β2 (R2) subunit of the class 1a Escherichia coli ribonucleotide reductases by reaction with O2 followed by one-electron reduction yields a spin-coupled, paramagnetic Fe(III)/Fe(IV) intermediate, denoted X, whose identity has been sought by multiple investigators for over a quarter of a century. To determine the(More)
We have employed EPR and a set of recently developed electron nuclear double resonance (ENDOR) spectroscopies to characterize a suite of [2Fe–2S] ferredoxin clusters from Aquifex aeolicus (Aae Fd1, Fd4, and Fd5). Antiferromagnetic coupling between the FeII, S = 2, and FeIII, S = 5/2, sites of the [2Fe–2S]+ cluster in these proteins creates an S = 1/2 ground(More)