Characterization of histidine coordination in VO{sup 2+}-substituted D-xylose isomerase by orientationally-selected electron spin-echo envelope modulation spectroscopy
- Inst. of Chemical Kinetics and Combustion, Novosibirsk (USSR)
- Universitaet des Saarlandes, Homburg (Germany)
- Universitaet Muenster (Germany)
An orientationally-selected electron spin-echo envelope modulation (ESEEM) spectroscopy investigation was performed on VO{sup 2+} introduced into the high-affinity metal-binding site of D-xylose isomerase. The ESEEM spectra clearly reveal the presence of nitrogen ligands with hyperfine coupling A{sup N} {approx} 6 MHz. Detailed analysis includes first- and second-order treatment of the nitrogen basic and combination harmonics in two-pulse ESEEM spectra of the g{sub {parallel}} and g{sub {perpendicular}} components. Complete determination of the hyperfine and quadrupole tensor indicates equatorial coordination of the imine nitrogen of the histidine residue. The presence of Cd{sup 2+} ion in the second, low-affinity metal-binding site does not affect the nitrogen couplings. The protons surrounding the VO{sup 2+} ion have been examined via the proton sum combinations in four-pulse ESEEM. They demonstrate the contribution of two protons probably belonging to the histidine ligand. These investigations strongly support the further application of VO{sup 2+} as a spin probe in conjunction with ESEEM spectroscopy for detailed investigation of nitrogen ligands in the active metal sites of proteins. 41 refs., 8 figs., 2 tabs.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC06-76RL01830; FG06-89ER75522; FG06-92RL12451
- OSTI ID:
- 50488
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 17 Vol. 117; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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