Structural polymorphism in bacterial EspA filaments revealed by cryo-EM and an improved approach to helical reconstruction.
Structural polymorphism in bacterial EspA filaments revealed by cryo-EM and an improved approach to helical reconstruction.
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通过冷冻电镜揭示细菌 EspA 丝的结构多态性和螺旋重建的改进方法。
DOI：
10.1016/j.str.2006.05.018
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Egelman,EdwardH
中科院分区：
文献类型：
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作者：
Wang,YingA;Yu,Xiong;Yip,Calvin;Strynadka,NatalieC;Egelman,EdwardH
从螺旋聚合物的电子显微 (EM) 图像进行三维重建的传统傅立叶-贝塞尔方法涉及对细丝进行平均，假设均匀结构和对称性。我们使用真实空间重建方法来研究肠致病性大肠杆菌形成的 EspA 丝。在阴性染色中，这些细丝的对称性是不明确的，我们认为这种不明确性可能比人们意识到的更为普遍。使用冷冻水合细丝的冷冻电镜，我们发现这些细丝具有每圈 5.6 个亚基的固定扭曲，但每个亚基的轴向上升量从约 3.6 Å 到 5.6 Å 不等。 〜15 Å 分辨率的重建显示，在中空腔周围假定的 α 螺旋堆积中，更压缩和延伸的细丝之间存在切换。在晶体之外，没有任何东西可以维持长程有序，螺旋聚合物的结构多态性可能比假设的要大得多。
The traditional Fourier-Bessel approach to three-dimensional reconstruction from electron microscopic (EM) images of helical polymers involves averaging over filaments, assuming a homogeneous structure and symmetry. We have used a real-space reconstruction approach to study the EspA filaments formed by enteropathogenicE. coli.In negative stain, the symmetry of these filaments is ambiguous, and we suggest that such ambiguities may be more prevalent than realized. Using cryo-EM of frozen-hydrated filaments, we find that these filaments have a fixed twist with 5.6 subunits per turn but an axial rise per subunit that varies from about 3.6 Å to 5.6 Å. Reconstructions at ∼15 Å resolution show a switching between the more compressed and extended filaments in the packing of putative α helices around the hollow lumen. Outside of a crystal, where there is nothing to maintain long-range order, the structural polymorphism in helical polymers may be much greater than has been assumed.