题目：High-Valent Iron: Nature\'s Sniper for Remote Specific Oxidation
报告人：Prof. Dr. Aimin Liu, Department of Chemistry, Georgia State University
时间：11月6日（周四），上午10:00
地点：化学楼5楼518会议室
邀请人：颜德岳教授（beat365）

报告摘要：

In recent years, it has come to light that many crucial biological processes are often mediated by some of the culprits, activated oxygen species and free radicals, which have been implicated in aging and oxidative stress. The dual roles of these reactive species as the leading cause of non-specific cell damage and as useful catalytic intermediates in biochemical reactions necessitate that their use in biological systems should be highly specific and strictly controlled. In particular, radical generation and long-range electron transfer as a means to transport oxidizing equivalents is increasingly regarded as an effective strategy for biological systems to perform demanding redox reactions in a controlled manner. One such example is the biosynthesis of tryptophan tryptophylquinone (TTQ), the catalytic center of methylamine dehydrogenase (MADH). TTQ is formed through posttranslational modification catalyzed by MauG, an enzyme which employs two c-type hemes to catalyze the oxidation of a tryptophan residue and a mono-hydroxylated tryptophan residue of a precursor protein, preMADH. The MauG-catalyzed reaction is a three-step, six-electron oxidation process. Each step requires one equivalent of H₂O₂ as the oxidant.

We have previously shown that an unprecedented high-valence bis-Fe(IV) intermediate of MauG orchestrates the oxidative production of TTQ (1,2). From our most recent EPR study, a novel tryptophan-based di-radical intermediate has been captured in the substrate protein preMADH as a result of oxidation by the bis-Fe(IV) species (3) In this presentation, a long-range remote catalysis mechanism will be presented and discussed.

References:
1. Li, Fu, Lee, Krebs, Davidson, Liu (2008) A catalytic di-heme bis-Fe(IV) intermediate, alternative to an Fe(IV)=O porphyrin radical, Proc. Natl. Acad. Sci. USA 105, 8597-8600.
2. Geng, Dornevil, Davidson, Liu (2013) Tryptophan-mediated charge-resonance stabilization in the bis-Fe(IV) redox state of MauG, Proc. Natl. Acad. Sci. USA 110, 9639-9644.
3. Yukl, Liu, Krzystek, Shin, Jensen, Davidson, Wilmot, Liu (2013) Diradical intermediate within the context of tryptophan tryptophylquinone biosynthesis, Proc. Natl. Acad. Sci. USA 110, 4569-4573.