BACKGROUND Type IV pili are widely expressed among Gram-negative bacteria, where they are involved in biofilm formation, serve in the transfer of DNA, motility and in the bacterial attachment to various surfaces. Type IV pili in Shewanella oneidensis are also supposed to play an important role in extracellular electron transfer by the attachment to sediments containing electron acceptors and potentially forming conductive nanowires. RESULTS The potential nanowire type IV pilin PilBac1 from S. oneidensis was characterized by a combination of complementary structural methods and the atomic structure was determined at a resolution of 1.67 Å by X-ray crystallography. PilBac1 consists of one long N-terminal α-helix packed against four antiparallel β-strands, thus revealing the core fold of type IV pilins. In the crystal, PilBac1 forms a parallel dimer with a sodium ion bound to one of the monomers. Interestingly, our PilBac1 crystal structure reveals two unusual features compared to other type IVa pilins: an unusual position of the disulfide bridge and a straight α-helical section, which usually exhibits a pronounced kink. This straight helix leads to a distinct packing in a filament model of PilBac1 based on an EM model of a Neisseria pilus. CONCLUSIONS In this study we have described the first structure of a pilin from Shewanella oneidensis. The structure possesses features of the common type IV pilin core, but also exhibits significant variations in the α-helical part and the D-region.

中文翻译：

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高分辨率结构的金属还原性细菌Shewanella oneidensis的IV型菌毛蛋白。

背景技术IV型菌毛在革兰氏阴性细菌中广泛表达，其中它们参与生物膜形成，用于DNA的转移，运动以及细菌附着于各种表面。人们还认为，印度希瓦氏菌中的IV型菌毛通过附着于含有电子受体的沉积物并可能形成导电纳米线，在细胞外电子转移中也起着重要作用。结果通过互补结构方法的结合对潜在的来自沙门氏菌的纳米线Ⅳ型菌毛蛋白PilBac1进行了表征，并通过X射线晶体学测定了1.67Å的原子结构。PilBac1由一个长的N末端α-螺旋组成，堆积在四个反平行的β链上，从而揭示了IV型菌毛的核心折叠。在水晶里 PilBac1形成平行二聚体，其中钠离子与单体之一结合。有趣的是，与其他IVa型菌毛蛋白相比，我们的PilBac1晶体结构显示出两个不寻常的特征：二硫键的不寻常位置和直的α螺旋形截面（通常表现出明显的扭结）。这种笔直的螺旋线导致基于尼尔森菌的EM模型的PilBac1丝模型中的独特堆积。结论在这项研究中，我们描述了来自印度希瓦氏菌的菌毛蛋白的第一个结构。该结构具有普通IV型菌毛蛋白核的特征，但在α螺旋部分和D区域也显示出显着变化。二硫键的异常位置和平直的α螺旋截面，通常表现出明显的扭结。这种笔直的螺旋线导致基于尼尔森菌的EM模型的PilBac1丝模型中的独特堆积。结论在这项研究中，我们描述了来自印度希瓦氏菌的菌毛蛋白的第一个结构。该结构具有普通IV型菌毛蛋白核的特征，但在α螺旋部分和D区域也显示出显着变化。二硫键桥的不寻常位置和笔直的α螺旋形截面，通常表现出明显的扭结。这种笔直的螺旋线导致基于尼尔森菌的EM模型的PilBac1丝模型中的独特堆积。结论在这项研究中，我们描述了来自印度希瓦氏菌的菌毛蛋白的第一个结构。该结构具有普通IV型菌毛蛋白核的特征，但在α螺旋部分和D区域也显示出显着变化。