Department of Molecular Biophysics and Biochemistry, Yale School of Medicine, New Haven, United States.
Laboratory of Molecular and Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay.
Elife. 2020 Mar 11;9:e53672. doi: 10.7554/eLife.53672.
Spirochete bacteria, including important pathogens, exhibit a distinctive means of swimming via undulations of the entire cell. Motility is powered by the rotation of supercoiled 'endoflagella' that wrap around the cell body, confined within the periplasmic space. To investigate the structural basis of flagellar supercoiling, which is critical for motility, we determined the structure of native flagellar filaments from the spirochete by integrating high-resolution cryo-electron tomography and X-ray crystallography. We show that these filaments are coated by a highly asymmetric, multi-component sheath layer, contrasting with flagellin-only homopolymers previously observed in exoflagellated bacteria. Distinct sheath proteins localize to the filament inner and outer curvatures to define the supercoiling geometry, explaining a key functional attribute of this spirochete flagellum.
螺旋体细菌，包括重要的病原体，通过整个细胞的波动表现出独特的游动方式。运动是由超螺旋的“端鞭毛”的旋转提供动力的，这些鞭毛缠绕在细胞体周围，被限制在周质空间内。为了研究对运动至关重要的鞭毛超螺旋的结构基础，我们通过整合高分辨率冷冻电子断层扫描和 X 射线晶体学，确定了螺旋体的天然鞭毛丝的结构。我们表明，这些纤维被一层高度不对称的多组分鞘层所覆盖，与以前在出鞭毛细菌中观察到的仅由鞭毛蛋白组成的同聚物形成对比。不同的鞘蛋白定位于纤维的内、外弯曲处，以确定超螺旋的几何形状，这解释了这种螺旋体鞭毛的一个关键功能属性。
