Direct Demonstration of the Presence of Coordinated Sulfate in the Reaction Pathway of Arabidopsis thaliana Sulfite Oxidase Using 33S Labeling and ESEEM Spectroscopy

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• 作者：Andrei V. Astashkin ; Kayunta Johnson-Winters ; Eric L. Klein ; Robert S. Byrne ; Russ Hille ; Arnold M. Raitsimring ; John H. Enemark
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：November 28, 2007
• 年：2007
• 卷：129
• 期：47
• 页码：14800 - 14810
• 全文大小：240K
• 年卷期：v.129,no.47(November 28, 2007)
• ISSN：1520-5126

文摘

Sulfite oxidase from Arabidopsis thaliana has been reduced at pH = 6 with sulfite labeled with³³S (nuclear spin I = ³/₂), followed by reoxidation by ferricyanide to generate the Mo(V) state of the activecenter. To obtain information about the hyperfine interaction (hfi) of ³³S with Mo(V), continuous-wave electronparamagnetic resonance (EPR) and electron spin echo envelope modulation (ESEEM) experiments havebeen performed. The interpretation of the EPR and ESEEM spectra was facilitated by a theoretical analysisof the nuclear transition frequencies expected for the situation of the nuclear quadrupole interaction beingmuch stronger than the Zeeman and hyperfine interactions. The isotropic hfi constant of ³³S determined inthese experiments was about 3 MHz, which demonstrates the presence of coordinated sulfate in the sulfite-reduced low-pH form of the plant enzyme.