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Correlating EPR and X-ray structural analysis of arsenite-inhibited forms of aldehyde oxidoreductase.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
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2007 (English)In: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, Vol. 12, no 3, 353-366 p.Article in journal (Refereed) Published
Abstract [en]

Two arsenite-inhibited forms of each of the aldehyde oxidoreductases from Desulfovibrio gigas and Desulfovibrio desulfuricans have been studied by X-ray crystallog. and ESR (EPR) spectroscopy. The molybdenum site of these enzymes shows a distorted square-pyramidal geometry in which two ligands, a hydroxyl/water mol. (the catalytic labile site) and a sulfido ligand, have been shown to be essential for catalysis. Arsenite addn. to active as-prepd. enzyme or to a reduced desulfo form yields two different species called A and B, resp., which show different Mo(V) EPR signals. Both EPR signals show strong hyperfine and quadrupolar couplings with an arsenic nucleus, which suggests that arsenic interacts with molybdenum through an equatorial ligand. X-ray data of single crystals prepd. from EPR-active samples show in both inhibited forms that the arsenic atom interacts with the molybdenum ion through an oxygen atom at the catalytic labile site and that the sulfido ligand is no longer present. EPR and X-ray data indicate that the main difference between both species is an equatorial ligand to molybdenum which was detd. to be an oxo ligand in species A and a hydroxyl/water ligand in species B. The conclusion that the sulfido ligand is not essential to det. the EPR properties in both Mo-As complexes is achieved through EPR measurements on a substantial no. of randomly oriented chem. reduced crystals immediately followed by X-ray studies on one of those crystals. EPR satn. studies show that the electron transfer pathway, which is essential for catalysis, is not modified upon inhibition.

Place, publisher, year, edition, pages
2007. Vol. 12, no 3, 353-366 p.
Keyword [en]
Molybdenum, containing enzymes, Aldehyde oxidoreductase, Xanthine oxidase family, Electron paramagnetic resonance, X-ray
National Category
Chemical Sciences
URN: urn:nbn:se:uu:diva-10587DOI: 10.1007/s00775-006-0191-9PubMedID: 17139522OAI: oai:DiVA.org:uu-10587DiVA: diva2:38355
Available from: 2007-04-10 Created: 2007-04-10Bibliographically approved

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