Characterization of Shewanella oneidensis MtrC:: a cell-surface decaheme cytochrome involved in respiratory electron transport to extracellular electron acceptors
Characterization of Shewanella oneidensis MtrC:: a cell-surface decaheme cytochrome involved in respiratory electron transport to extracellular electron acceptors
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DOI：
10.1007/s00775-007-0278-y
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发表时间：
2007-09-01
影响因子：
3
通讯作者：
Richardson, David J.
中科院分区：
文献类型：
--
作者：
Hartshorne, Robert S.;Jepson, Brian N.;Richardson, David J.
MtrC 是一种十血红素 c 型细胞色素，与希瓦氏菌属 Fe(III) 呼吸物种的外细胞膜相关。据建议，它通过介导电子转移到可作为末端电子受体的细胞外矿物氧化物来在无氧呼吸中发挥作用。目前的工作首次使用从 Shewanella oneidensis MR-1 中纯化的蛋白质对 MtrC 进行分光电位和伏安表征。通过紫外可见吸收和电子顺磁共振 (EPR) 光谱监测的电位滴定表明，MtrC 内的血红素在约 +100 至约 -500 mV（相对于标准氢电极）的宽电位范围内滴定。跨过这个电位窗口，紫外可见吸收光谱是低自旋 c 型血红素的特征，EPR 光谱揭示了广泛、复杂的特征，表明存在磁自旋耦合的低自旋 c 型血红素。 MtrC 的非催化蛋白膜伏安法证明了在类似于光谱公开的电位窗口上的可逆电化学。伏安法还可以定义 MtrC 在与固体电极表面直接电子交换以及模型 Fe(III) 基质还原过程中的动力学特性。总而言之，这些数据提供了 MtrC 可以运营的潜在领域的定量信息。
MtrC is a decaheme c-type cytochrome associated with the outer cell membrane of Fe(III)-respiring species of the Shewanella genus. It is proposed to play a role in anaerobic respiration by mediating electron transfer to extracellular mineral oxides that can serve as terminal electron acceptors. The present work presents the first spectropotentiometric and voltammetric characterization of MtrC, using protein purified from Shewanella oneidensis MR-1. Potentiometric titrations, monitored by UV-vis absorption and electron paramagnetic resonance (EPR) spectroscopy, reveal that the hemes within MtrC titrate over a broad potential range spanning between approximately +100 and approximately -500 mV (vs. the standard hydrogen electrode). Across this potential window the UV-vis absorption spectra are characteristic of low-spin c-type hemes and the EPR spectra reveal broad, complex features that suggest the presence of magnetically spin-coupled low-spin c-hemes. Non-catalytic protein film voltammetry of MtrC demonstrates reversible electrochemistry over a potential window similar to that disclosed spectroscopically. The voltammetry also allows definition of kinetic properties of MtrC in direct electron exchange with a solid electrode surface and during reduction of a model Fe(III) substrate. Taken together, the data provide quantitative information on the potential domain in which MtrC can operate.