L型直鞭毛丝的结构与分子间相互作用
Structure and Intermolecular Interactions between L-Type Straight Flagellar Filaments.
作者信息
Louzon Daniel, Ginsburg Avi, Schwenger Walter, Dvir Tom, Dogic Zvonimir, Raviv Uri
机构信息
The Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, Israel; The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, Israel.
The Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, Israel; The Institute for Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel.
出版信息
Biophys J. 2017 May 23;112(10):2184-2195. doi: 10.1016/j.bpj.2017.02.038.
Bacterial mobility is powered by rotation of helical flagellar filaments driven by rotary motors. Flagellin isolated from the Salmonella Typhimurium SJW1660 strain, which differs by a point mutation from the wild-type strain, assembles into straight filaments in which flagellin monomers are arranged in a left-handed helix. Using small-angle x-ray scattering and osmotic stress methods, we investigated the structure of SJW1660 flagellar filaments as well as the intermolecular forces that govern their assembly into dense hexagonal bundles. The scattering data were fitted to models, which took into account the atomic structure of the flagellin subunits. The analysis revealed the exact helical arrangement and the super-helical twist of the flagellin subunits within the filaments. Under osmotic stress, the filaments formed two-dimensional hexagonal bundles. Monte Carlo simulations and continuum theories were used to analyze the scattering data from hexagonal arrays, revealing how the bundle bulk modulus and the deflection length of filaments in the bundles depend on the applied osmotic stress. Scattering data from aligned flagellar bundles confirmed the theoretically predicated structure-factor scattering peak line shape. Quantitative analysis of the measured equation of state of the bundles revealed the contributions of electrostatic, hydration, and elastic interactions to the intermolecular forces associated with bundling of straight semi-flexible flagellar filaments.
细菌的运动由旋转电机驱动的螺旋鞭毛丝的旋转提供动力。从鼠伤寒沙门氏菌SJW1660菌株中分离出的鞭毛蛋白，该菌株与野生型菌株存在一个点突变差异，其组装成直丝，其中鞭毛蛋白单体呈左手螺旋排列。我们使用小角X射线散射和渗透压方法，研究了SJW1660鞭毛丝的结构以及控制它们组装成致密六边形束的分子间力。散射数据与考虑了鞭毛蛋白亚基原子结构的模型进行拟合。分析揭示了丝内鞭毛蛋白亚基的确切螺旋排列和超螺旋扭曲。在渗透压下，丝形成二维六边形束。使用蒙特卡罗模拟和连续介质理论分析来自六边形阵列的散射数据，揭示了束的体积模量和束中丝的挠曲长度如何取决于施加的渗透压。来自排列的鞭毛束的散射数据证实了理论预测的结构因子散射峰线形状。对测得的束状态方程的定量分析揭示了静电、水合和弹性相互作用对与直的半柔性鞭毛丝束相关的分子间力的贡献。
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