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Lookup NU author(s): Dr Katsuko Sato,
Professor Christopher Dennison
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Copper-containing nitrite reductases (NiRs) possess type 1 (T1) and type 2 (T2) copper sites and can be either green or blue in color owing to differences at their T1 centers. The active sites of a green and a blue NiR were studied by utilizing their T1CuI/ T2CoII and T1CoII/ T2CoII-substituted forms. The UV/Vis spectra of these derivatives highlight the similarity of the T2 centers in these enzymes and that T1 site differences are also present in the CoII forms. The paramagnetic NMR spectra of T1CuI/T2CoII enzymes allow hyperfine shifted resonances from the three T2 His ligands to be as signed: these exhibit remarkably similar positions in the spectra of both NiRs, emphasizing the homology of the T2 centers. The addition of nitrite results in subtle alterations in the paramagnetic NMR spectra of the T1CuI/ T2Co II forms at pH < 7, which indicate a geometry change upon the binding of substrate. Shifted resonances from all of the T1 site ligands have been assigned and the CoII-N(His) interac tions are alike, whereas the CβH proton resonances of the Cys ligand exhibit subtle chemical shift differences in the blue and green NiRs. The strength of the axial CoII-S(Met) interaction is similar in the two NiRs studied, but the altered conformation of the side chain of this ligand results in a dramatically different chemical shift pattern for the CγH protons. This indicates an alteration in the bonding of the axial ligand in these derivatives, which could be influential in the CuII proteins. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.
Author(s): Sato K, Dennison C
Publication type: Article
Publication status: Published
Journal: Chemistry - A European Journal
ISSN (print): 0947-6539
ISSN (electronic): 1521-3765
Publisher: Wiley - VCH Verlag GmbH & Co. KGaA
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