Firer-Sherwood Mackenzie, Pulcu Gökçe Su, Elliott Sean J
Department of Chemistry, Boston University, 590 Commonwealth Ave., Boston, MA 02215, USA.
J Biol Inorg Chem. 2008 Aug;13(6):849-54. doi: 10.1007/s00775-008-0398-z. Epub 2008 Jun 25.
The multi-heme cytochromes from Shewanella oneidensis associated with the dissimilatory metal reduction (DMR) pathway have been investigated using the technique of protein film voltammetry (PFV). Using PFV, we have interrogated each of the multi-heme cytochromes (MtrA, STC, and solubilized versions of the membrane-bound proteins CymA, OmcA, and MtrC) under identical conditions for the first time. Each cytochrome reveals a broad envelope of voltammetric response, indicative of multiple redox cofactors that span a range of potential of approximately 300 mV. Our studies show that, when considered as an aggregate pathway, the multiple hemes of the DMR cytochromes provide a "window" of operating potential for electron transfer to occur from the cellular interior to the exterior spanning values of -250 to 0 mV (at circumneutral values of pH). Similarly, each cytochrome supports interfacial electron transfer at rates on the order of 200 s(-1). These data are taken together to suggest a model of electron transport where a wide window of potential allows for charge transfer from the cellular interior to the exterior to support bioenergetics.
利用蛋白质膜伏安法（PFV）技术，对与异化金属还原（DMR）途径相关的来自希瓦氏菌的多血红素细胞色素进行了研究。通过PFV，我们首次在相同条件下对每种多血红素细胞色素（MtrA、STC以及膜结合蛋白CymA、OmcA和MtrC的可溶形式）进行了检测。每种细胞色素都显示出一个宽泛的伏安响应包络，表明存在多个氧化还原辅因子，其电位范围约为300 mV。我们的研究表明，当被视为一个聚集途径时，DMR细胞色素的多个血红素为电子从细胞内部转移到外部提供了一个“操作电位窗口”，其跨度为-250至0 mV（在pH值为中性时）。同样，每种细胞色素都以约200 s⁻¹的速率支持界面电子转移。综合这些数据，我们提出了一个电子传输模型，其中一个宽的电位窗口允许电荷从细胞内部转移到外部以支持生物能量学。
