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Isolation and spectroscopic characterization of the membrane-bound nitrate reductase from Pseudomonas chlororaphis DSM 50135
- Source :
-
BBA - General Subjects . May2005, Vol. 1723 Issue 1-3, p151-162. 12p. - Publication Year :
- 2005
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Abstract
- Abstract: A nitrate reductase was solubilized with Triton X-100 from the membranes of Pseudomonas chlororaphis DSM 50135 grown microaerobically in the presence of nitrate. Like other membrane-bound nitrate reductases, it contains three subunits, of 129, 66 (64) and 24 kDa, referred to in the literature as α, β and γ, respectively. Electrocatalytic studies revealed that only the membrane-bound, not the solubilized form of the enzyme, can accept electrons from a menaquinone analog, menadione, whereas both forms can accept electrons from methylviologen. The isolated enzyme possesses several iron–sulfur clusters and a molybdopterin guanine dinucleotide active center. The iron–sulfur clusters can be grouped in two classes according to their redox properties, the high-potential and low-potential clusters. In the as-isolated enzyme, two forms of the molybdenum center, high- and low-pH, are detectable by electron paramagnetic resonance spectroscopy. The low-pH form shows a hyperfine splitting due to a proton, suggesting the presence of an –OHx ligand. Dithionite reduces the Mo(V) center to Mo(IV) and subsequent reoxidization with nitrate originates a new Mo(V) signal, identical to the oxidized low-pH form but lacking its characteristic hyperfine splitting. The isolated preparation also contains heme c (in a sub-stoichiometric amount) with the ability to relay electrons to the molybdenum center, suggesting that this nitrate reductase may contain heme c instead of the heme b usually found in this class of enzymes. [Copyright &y& Elsevier]
- Subjects :
- *GLUTATHIONE
*CHROMIUM group
*TRANSITION metals
*PARTICLES (Nuclear physics)
Subjects
Details
- Language :
- English
- ISSN :
- 03044165
- Volume :
- 1723
- Issue :
- 1-3
- Database :
- Academic Search Index
- Journal :
- BBA - General Subjects
- Publication Type :
- Academic Journal
- Accession number :
- 18512704
- Full Text :
- https://doi.org/10.1016/j.bbagen.2005.02.008