Three-dimensional structure of the Neisseria meningitidis secretin PilQ determined from negative-stain transmission electron microscopy
Three-dimensional structure of the Neisseria meningitidis secretin PilQ determined from negative-stain transmission electron microscopy
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DOI：
10.1128/jb.185.8.2611-2617.2003
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发表时间：
2003-04-01
影响因子：
3.2
通讯作者：
Derrick, JP
中科院分区：
文献类型：
--
作者：
Collins, RF;Ford, RC;Derrick, JP
来自致病菌脑膜炎奈瑟菌的 PiIQ 促胰液素是一种完整的外膜蛋白复合物，在 IV 型菌毛的生物发生中发挥着至关重要的作用。我们在这里展示了这种类型促胰液素的第一个三维结构，分辨率为 2.5 nm，通过应用于负染色中可视化的纯化蛋白质复合物的单粒子平均方法获得。在投影中，PiIQ 复合体是圆形的，具有类似甜甜圈的外观。从侧面看，它具有圆形圆锥形轮廓。该复合物被证明具有 12 重旋转对称性，并且该属性用于通过对称平均来提高密度图的质量。该结构的主要特征是分子中心内有一个 10 nm 深的空腔。该空腔的横截面呈漏斗形，复合物顶部的直径为 6.5 nm，并逐渐变细至封闭点，有效阻止了穿过 PiIQ 复合物的连续孔的形成。这些结果表明，复合物必须经历构象变化才能容纳穿过外膜的直径为 6.5 nm 的组装菌毛纤维。
The PiIQ secretin from the pathogenic bacterium Neisseria meningitidis is an integral outer membrane protein complex which plays a crucial role in the biogenesis of type IV pili. We present here the first three-dimensional structure of this type of secretin at 2.5-nm resolution, obtained by single-particle averaging methods applied to the purified protein complex visualized in a negative stain. In projection, the PiIQ complex is circular, with a donut-like appearance. When viewed from the side it has a rounded, conical profile. The complex was demonstrated to have 12-fold rotational symmetry, and this property was used to improve the quality of the density map by symmetry averaging. The dominant feature of the structure is a cavity, 10 nm deep, within the center of the molecule. The cavity is funnel-shaped in cross section, measures 6.5 nm in diameter at the top of the complex, and tapers to a closed point, effectively blocking formation of a continuous pore through the PiIQ complex. These results suggest that the complex would have to undergo a conformational change in order to accommodate an assembled pilus fiber of diameter 6.5 nm running through the outer membrane.