An NMR structural study of nickel-substituted rubredoxin |
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Authors: | Brian J. Goodfellow Iven C. N. Duarte Anjos L. Macedo Brian F. Volkman Sofia G. Nunes I. Moura John L. Markley José J. G. Moura |
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Affiliation: | 1. CICECO, Departamento de Química, Universidade Aveiro, 3810-193, Aveiro, Portugal 2. REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal 3. Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, 53226, USA 4. Valencia Infertility Institute (IVI), Valencia, Spain 5. Department of Biochemistry, 171A Biochemistry Addition, University of Wisconsin, 433 Babcock Drive, Madison, WI, 53706-1544, USA
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Abstract: | The Ni(II) and Zn(II) derivatives of Desulfovibrio vulgaris rubredoxin (DvRd) have been studied by NMR spectroscopy to probe the structure at the metal centre. The βCH2 proton pairs from the cysteines that bind the Ni(II) atom have been identified using 1D nuclear Overhauser enhancement (NOE) difference spectra and sequence specifically assigned via NOE correlations to neighbouring protons and by comparison with the published X-ray crystal structure of a Ni(II) derivative of Clostridium pasteurianum rubredoxin. The solution structures of DvRd(Zn) and DvRd(Ni) have been determined and the paramagnetic form refined using pseudocontact shifts. The determination of the magnetic susceptibility anisotropy tensor allowed the contact and pseudocontact contributions to the observed chemical shifts to be obtained. Analysis of the pseudocontact and contact chemical shifts of the cysteine Hβ protons and backbone protons close to the metal centre allowed conclusions to be drawn as to the geometry and hydrogen-bonding pattern at the metal binding site. The importance of NH–S hydrogen bonds at the metal centre for the delocalization of electron spin density is confirmed for rubredoxins and can be extrapolated to metal centres in Cu proteins: amicyanin, plastocyanin, stellacyanin, azurin and pseudoazurin. |
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