Kelly D Daughtry, Youli Xiao, Deborah Stoner-Ma, Eunsun Cho, Allen M Orville, Pinghua Liu, Karen N Allen
Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02218, USA.
Journal of the American Chemical Society 2012 Feb 8Herein, 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.
Kelly D Daughtry, Youli Xiao, Deborah Stoner-Ma, Eunsun Cho, Allen M Orville, Pinghua Liu, Karen N Allen. Quaternary ammonium oxidative demethylation: X-ray crystallographic, resonance Raman, and UV-visible spectroscopic analysis of a Rieske-type demethylase. Journal of the American Chemical Society. 2012 Feb 8;134(5):2823-34
PMID: 22224443
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