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首页> 外文期刊>Biochemistry >Carboxyl group of glu113 is required for stabilization of the diferrous and bis-FeIV states of MauG
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Carboxyl group of glu113 is required for stabilization of the diferrous and bis-FeIV states of MauG

机译：Glu113的羧基对于稳定MauG的二亚铁和双FeIV态是必需的

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摘要

The diheme enzyme MauG catalyzes a six-electron oxidation required for post-translational modification of a precursor of methylamine dehydrogenase (preMADH) to complete the biosynthesis of its protein-derived tryptophan tryptophylquinone (TTQ) cofactor. Crystallographic studies have implicated Glu113 in the formation of the bis-Fe~(IV) state of MauG, in which one heme is Fe~(IV)? - "O and the other is Fe~(IV) with His-Tyr axial ligation. An E113Q mutation had no effect on the structure of MauG but significantly altered its redox properties. E113Q MauG could not be converted to the diferrous state by reduction with dithionite but was only reduced to a mixed valence FeII/FeIII state, which is never observed in wild-type (WT) MauG. Addition of H_2O_2 to E113Q MauG generated a high valence state that formed more slowly and was less stable than the bis-Fe~(IV) state of WT MauG. E113Q MauG exhibited no detectable TTQ biosynthesis activity in a steady-state assay with preMADH as the substrate. It did catalyze the steady-state oxidation of quinol MADH to the quinone, but 1000-fold less efficiently than WT MauG. Addition of H _2O_2 to a crystal of the E113Q MauG-preMADH complex resulted in partial synthesis of TTQ. Extended exposure of these crystals to H_2O_2 resulted in hydroxylation of Pro107 in the distal pocket of the high-spin heme. It is concluded that the loss of the carboxylic group of Glu113 disrupts the redox cooperativity between hemes that allows rapid formation of the diferrous state and alters the distribution of high-valence species that participate in charge-resonance stabilization of the bis-Fe IV redox state.
机译：双血红素酶MauG催化甲胺脱氢酶（preMADH）前体的翻译后修饰所需的六电子氧化，以完成其蛋白质衍生色氨酸色氨酸醌（TTQ）辅因子的生物合成。晶体学研究表明Glu113参与了MauG的双Fe〜（IV）状态的形成，其中一个血红素是Fe〜（IV）？ -“ O和另一个是带有His-Tyr轴向连接的Fe〜（IV）。E113Q突变对MauG的结构没有影响，但显着改变了其氧化还原特性。连二亚硫酸盐，但仅还原为FeII / FeIII混合价态，这在野生型（MauG）MauG中从未观察到。向E113Q MauG中添加H_2O_2生成的高价态比二甲基亚砜更慢且不稳定。 WT MauG的Fe〜（IV）状态E113Q MauG在以preMADH为底物的稳态测定中没有可检测到的TTQ生物合成活性，它确实催化了quinol MADH稳态氧化为醌，但减少了1000倍在E113Q MauG-preMADH络合物的晶体中添加H _2O_2会导致TTQ的部分合成，这些晶体长时间暴露于H_2O_2会导致高自旋血红素远端囊中Pro107的羟基化。得出的结论是f Glu113的羧基破坏了血红素之间的氧化还原协同作用，从而允许快速形成二亚铁态，并改变了参与双Fe IV氧化还原态电荷共振稳定化的高价物质的分布。

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