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Proton Nuclear Magnetic Resonance Investigation of the [2Fe-2S]1--Containing “Rieske-Type” Protein from Xanthobacter Strain Py2
  • Richard C. Holz, Marquette University
  • Frederick J. Small, Utah State University
  • Scott A. Ensign, Utah State University
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Proton NMR spectra of the Rieske-type ferredoxin from Xanthobacter strain Py2 were recorded in both H2O and D2O buffered solutions at pH 7.2. Several well-resolved hyperfine-shifted 1H NMR signals were observed in the 90 to −20 ppm chemical shift range. Comparison of spectra recorded in H2O and D2O buffered solutions indicated that the signals at −11.4 (L) and −15.5 (M) ppm were solvent-exchangeable and thus were assigned to the two histidine Nε2H protons. The remaining observed signals were assigned based upon chemical shift, T1 values, and one-dimensional nuclear Overhauser effect (nOe) saturation transfer experiments to either CβH or CαH protons of cluster cysteinyl or histidine ligands. Upon oxidation of the [2Fe-2S] cluster, only two broad resonances were observed, indicating that the two Fe(III) ions are strongly antiferromagnetically coupled. In addition, the temperature dependence of each observed hyperfine-shifted signal in the reduced state was determined, providing information about the magnetic properties of the [2Fe-2S]1- cluster. Fits of the temperature data observed for each resonance to equations describing the hyperfine shift with their Boltzmann weighting factors provided a ΔEL value of 185 ± 26 cm-1 which, in turn, gives −2J as 124 cm-1. These data indicate that the two iron centers in the reduced [2Fe-2S] Rieske-type center are moderately antiferromagnetically coupled. The combination of these data with the available spectroscopic and crystallographic results for Rieske-type proteins has provided new insights into the role of the Rieske-type protein from Xanthobacter strain Py2 in alkene oxidation.

Biochemistry, Vol. 36, No. 48 (December 2, 1997): 14690-14696. DOI.

Richard Holz was affiliated with the Utah State University at the time of publication.

Citation Information
Richard C. Holz, Frederick J. Small and Scott A. Ensign. "Proton Nuclear Magnetic Resonance Investigation of the [2Fe-2S]1--Containing “Rieske-Type” Protein from Xanthobacter Strain Py2" Biochemistry (1997) ISSN: 0006-2960
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