微生物纳米线的结构揭示了堆叠的血红素，这些血红素可以在微米尺度上传输电子。
Structure of Microbial Nanowires Reveals Stacked Hemes that Transport Electrons over Micrometers.
机构信息
Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
Microbial Sciences Institute, Yale University, New Haven, CT 06516, USA; Department of Molecular, Cellular & Developmental Biology, Yale University, New Haven, CT 06511, USA.
出版信息
Cell. 2019 Apr 4;177(2):361-369.e10. doi: 10.1016/j.cell.2019.03.029.
Long-range (>10 μm) transport of electrons along networks of Geobacter sulfurreducens protein filaments, known as microbial nanowires, has been invoked to explain a wide range of globally important redox phenomena. These nanowires were previously thought to be type IV pili composed of PilA protein. Here, we report a 3.7 Å resolution cryoelectron microscopy structure, which surprisingly reveals that, rather than PilA, G. sulfurreducens nanowires are assembled by micrometer-long polymerization of the hexaheme cytochrome OmcS, with hemes packed within ∼3.5-6 Å of each other. The inter-subunit interfaces show unique structural elements such as inter-subunit parallel-stacked hemes and axial coordination of heme by histidines from neighboring subunits. Wild-type OmcS filaments show 100-fold greater conductivity than other filaments from a ΔomcS strain, highlighting the importance of OmcS to conductivity in these nanowires. This structure explains the remarkable capacity of soil bacteria to transport electrons to remote electron acceptors for respiration and energy sharing.
长程（>10μm）电子沿着已知的能够进行全球范围内各种重要氧化还原反应的硫还原地杆菌蛋白丝（即微生物纳米线）网络进行传输的现象，被用来解释这一现象。这些纳米线以前被认为是由 PilA 蛋白组成的 IV 型菌毛。在这里，我们报告了一个 3.7Å 分辨率的冷冻电子显微镜结构，结果令人惊讶地表明，硫还原地杆菌纳米线不是由 PilA 组装而成，而是由六血红素细胞色素 OmcS 组装成的长达数微米的聚合物，彼此之间的血红素之间的间隔约为 3.5-6Å。亚基间界面显示出独特的结构元件，例如亚基间平行堆叠的血红素和来自相邻亚基的组氨酸对血红素的轴向配位。野生型 OmcS 纤维的导电性比来自ΔomcS 菌株的其他纤维高 100 倍，这突出了 OmcS 在这些纳米线中对导电性的重要性。该结构解释了土壤细菌将电子输送到远程电子受体进行呼吸和能量共享的非凡能力。
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