Download MendeleyQuaternary Ammonium Oxidative Demethylation: X-ray Crystallographic, Resonance Raman, and UV-Visible Spectroscopic Analysis of a Rieske-Type Demethylase.
Daughtry, K.D., Xiao, Y., Stoner-Ma, D., Cho, E., Orville, A.M., Liu, P., Allen, K.N.(2012) J Am Chem Soc 134: 2823-2834
- PubMed: 22224443
- DOI: https://doi.org/10.1021/ja2111898
- Primary Citation of Related Structures:
3VCA, 3VCP - PubMed Abstract:
Herein, the structure resulting from in situ turnover in a chemically challenging quaternary ammonium oxidative demethylation reaction was captured via crystallographic analysis and analyzed via single-crystal spectroscopy. Crystal structures were determined for the Rieske-type monooxygenase, stachydrine demethylase, in the unliganded state (at 1.6 Å resolution) and in the product complex (at 2.2 Å resolution). The ligand complex was obtained from enzyme aerobically cocrystallized with the substrate stachydrine (N,N-dimethylproline). The ligand electron density in the complex was interpreted as proline, generated within the active site at 100 K by the absorption of X-ray photon energy and two consecutive demethylation cycles. The oxidation state of the Rieske iron-sulfur cluster was characterized by UV-visible spectroscopy throughout X-ray data collection in conjunction with resonance Raman spectra collected before and after diffraction data. Shifts in the absorption band wavelength and intensity as a function of absorbed X-ray dose demonstrated that the Rieske center was reduced by solvated electrons generated by X-ray photons; the kinetics of the reduction process differed dramatically for the liganded complex compared to unliganded demethylase, which may correspond to the observed turnover in the crystal.
Organizational Affiliation:
Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02218, USA.
