Rapid electron exchange between surface-exposed bacterial cytochromes and Fe(III) minerals
Rapid electron exchange between surface-exposed bacterial cytochromes and Fe(III) minerals
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DOI：
10.1073/pnas.1220074110
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发表时间：
2013-04-16
影响因子：
11.1
通讯作者：
Clarke, Thomas A.
中科院分区：
文献类型：
--
作者：
White, Gaye F.;Shi, Zhi;Clarke, Thomas A.
矿物呼吸细菌希瓦氏杆菌使用一种蛋白质复合物MtrCAB，由两种十碳胺细胞色素MtrC和MtrA组成，聚集在一个跨膜孔蛋白MtrB内，将电子穿过外膜传递到各种矿物基电子受体。一个含有内在化电子载体池的蛋白质脂质体系统被用来研究MtrCAB复合物的拓扑结构与其通过脂质双分子层向外部定位的Fe（III）氧化物传输电子的能力之间的关系。MtrA面向磷脂双分子层内部，MtrC暴露在磷脂双分子层的外表面，证明了在体内建立的定向，电子通过MtrCAB从内部电子载流子池转移到固相Fe（III）氧化物。其还原针铁矿、赤铁矿和鳞球石的速率是文献报道的10(3)倍，反应速率的顺序与在oneidensis培养中观察到的一致。相比之下，纯化的MtrC和Fe（III）氧化物之间的单次转化反应的确定速率低10(3)倍。通过提供连续的电子流动，蛋白质脂质体实验证明，通过trcab直接传导到Fe（III）氧化物足以支持体内厌氧固相铁呼吸。
The mineral-respiring bacterium Shewanella oneidensis uses a protein complex, MtrCAB, composed of two decaheme cytochromes, MtrC and MtrA, brought together inside a transmembrane porin, MtrB, to transport electrons across the outer membrane to a variety of mineral-based electron acceptors. A proteoliposome system containing a pool of internalized electron carriers was used to investigate how the topology of the MtrCAB complex relates to its ability to transport electrons across a lipid bilayer to externally located Fe(III) oxides. With MtrA facing the interior and MtrC exposed on the outer surface of the phospholipid bilayer, the established in vivo orientation, electron transfer from the interior electron carrier pool through MtrCAB to solid-phase Fe(III) oxides was demonstrated. The rates were 10(3) times higher than those reported for reduction of goethite, hematite, and lepidocrocite by S. oneidensis, and the order of the reaction rates was consistent with those observed in S. oneidensis cultures. In contrast, established rates for single turnover reactions between purified MtrC and Fe(III) oxides were 10(3) times lower. By providing a continuous flow of electrons, the proteoliposome experiments demonstrate that conduction through MtrCAB directly to Fe(III) oxides is sufficient to support in vivo, anaerobic, solid-phase iron respiration.