Effects of soluble flavin on heterogeneous electron transfer between surface-exposed bacterial cytochromes and iron oxides
Effects of soluble flavin on heterogeneous electron transfer between surface-exposed bacterial cytochromes and iron oxides
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DOI：
10.1016/j.gca.2015.03.039
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发表时间：
2015-08-15
影响因子：
5
通讯作者：
Zachara, John M.
中科院分区：
文献类型：
--
作者：
Wang, Zheming;Shi, Zhi;Zachara, John M.
异化铁还原菌在厌氧条件下可以利用不溶性的铁（锰）氧化物作为末端电子受体。特别是对于希瓦氏菌属物种，有证据表明铁还原与黄素单核苷酸（FMN）和核黄素的分泌有关。然而，黄素参与的确切机制尚不清楚;而一些人指出黄素介导电子转移（Marsili等人，2008），其他人指出黄素作为外膜蛋白的辅因子（Okamoto等人，2013年）。在这项工作中，我们使用甲基紫精（MV中心点+）封装，孔蛋白-细胞色素复合物（MtrCAB）嵌入脂质体（MEL）作为希瓦氏菌外膜的合成模型，以研究微生物产生的黄素的介导行为。MEL（[ MV中心点+]）对针铁矿、赤铁矿和纤铁矿（200 μ M）的还原动力学与40 μ M和MtrABC针铁矿相似，与它们的还原电位相同，这意味着热力学控制反应速率。对于LEP，具有最高的还原电位之间的三个Fe（III）-氧化物，其还原FMNH 2完成在不到10分钟，这表明FMN是能够介导电子转移到LEP。在较高的FMN浓度（>1 μ M），两个步骤的反应速率下降，并与FMN浓度成反比，表明FMN抑制MEL的Fe（III）-氧化物的电子转移反应在这些条件下。所观察到的动力学行为，黄素介导的Fe（III）-氧化物还原在自然环境中的影响进行了讨论。(C)2015爱思唯尔有限公司版权所有。
Dissimilatory iron-reducing bacteria can utilize insoluble Fe(Mn)-oxides as a terminal electron acceptor under anaerobic conditions. For Shewanella species specifically, evidence suggests that iron reduction is associated with the secretion of flavin mononucleotide (FMN) and riboflavin. However, the exact mechanism of flavin involvement is unclear; while some indicate that flavins mediate electron transfer (Marsili et al., 2008), others point to flavin serving as co-factors to outer membrane proteins (Okamoto et al., 2013). In this work, we used methyl viologen (MV center dot+)-encapsulated, porin-cytochrome complex (MtrCAB) embedded liposomes (MELs) as a synthetic model of the Shewanella outer membrane to investigate the proposed mediating behavior of microbially produced flavins. The reduction kinetics of goethite, hematite and lepidocrocite (200 mu M) by MELs ([ MV center dot+] similar to 40 mu M and MtrABC goethite, the same as their reduction potentials, implying thermodynamic control on reaction rate. For LEP, with the highest reduction potential among the three Fe(III)-oxides, its reduction by FMNH2 was completed in less than 10 min, suggesting that FMN was capable of mediating electron transfer to LEP. At higher FMN concentrations (>1 mu M), the reaction rates for both steps decreased and varied inversely with FMN concentration, indicating that FMN inhibited the MEL to Fe(III)-oxide electron transfer reaction under these conditions. The implications of the observed kinetic behaviors to flavin-mediated Fe(III)-oxide reduction in natural environments are discussed. (C) 2015 Elsevier Ltd. All rights reserved.