Proton Nuclear Magnetic Resonance Investigation of the [2Fe-2S]^1--Containing “Rieske-Type” Protein from Xanthobacter Strain Py2

Authors

Richard C. Holz, Marquette UniversityFollow
Frederick J. Small, Utah State University
Scott A. Ensign, Utah State University

Document Type

Article

Publication Date

12-2-1997

Source Publication

Biochemistry

Source ISSN

0006-2960

Abstract

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 N^ε2H 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 C^βH or C^αH 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 ΔE_L 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.

Comments

Accepted version. Biochemistry, Vol. 36, No. 48 (December 2, 1997): 14690-14696. DOI. © 1997 American Chemical Society Publications. Used with permission.

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

Recommended Citation

Holz, Richard C.; Small, Frederick J.; and Ensign, Scott A., "Proton Nuclear Magnetic Resonance Investigation of the [2Fe-2S]^1--Containing “Rieske-Type” Protein from Xanthobacter Strain Py2" (1997). Chemistry Faculty Research and Publications. 303.
https://epublications.marquette.edu/chem_fac/303