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首页> 外文期刊>Journal of Molecular Biology >STRUCTURE OF BACTERIAL FLAGELLAR FILAMENTS AT 11 ANGSTROM RESOLUTION - PACKING OF THE ALPHA-HELICES
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STRUCTURE OF BACTERIAL FLAGELLAR FILAMENTS AT 11 ANGSTROM RESOLUTION - PACKING OF THE ALPHA-HELICES

机译：细菌ST丝的结构在11角分辨率下-阿尔法-头的包装

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摘要

Recent advances in the analysis of electron micrographs of frozen, hydrated bacterial filaments have allowed us to average data from more than 150 images and to reconstruct the bacterial flagellar filament of Salmonella typhimurium at a resolution of similar to 11 Angstrom. In addition to the outermost features seen in earlier lower resolution maps of the filament, we find a pair of concentric tubes which surround a similar to 30 Angstrom diameter channel at the center of the structure. The walls of these tubes are composed of rod-like features which we have interpreted as columns of individual alpha-helices stacked end-to-end. Each column runs approximately parallel to the helix axis. The wall of the innermost tube, at a radius of similar to 20 Angstrom, is formed from II such columns. The wall of the second tube is formed from 22 columns which occur alternately at radii of similar to 43 and similar to 47 Angstrom. The two concentric tubes are held apart by spacers. These are short, rod-like features, which run approximately parallel to the helix axis. We have interpreted these as additional cl-helices. By symmetry each flagellin monomer contributes an alpha-helix to the inner tube, two alpha-helices to the outer tube and a fourth alpha-helix to the spacer. We have tentatively assigned one type of alpha-helix in the outer tube to the similar to 30 C-terminal residues of flagellin while the remaining three alpha-helices are assigned to the similar to 70 N-terminal residues. This interpretation of the reconstruction is consistent with available biochemical, biophysical and amino acid sequence information. We also present details of improved methodology to extract and evaluate the original data and also to assess the statistical significance of features in the three-dimensional map. [References: 49]
机译：冷冻，水合细菌细丝的电子显微照片分析的最新进展使我们能够对150幅以上图像的数据进行平均，并以类似于11埃的分辨率重建鼠伤寒沙门氏菌的细菌鞭毛细丝。除了在较早的较低分辨率的细丝图中看到的最外层特征之外，我们还发现了一对同心管，它们围绕结构中心的直径类似于30埃的通道。这些管的壁由杆状特征组成，我们将其解释为端对端堆叠的单个α螺旋的列。每列大致平行于螺旋轴。最里面的管的壁，其半径类似于20埃，是由II这样的柱子形成的。第二管的壁由22个柱形成，这些柱交替出现在半径近似为43和47埃之间。两个同心管通过垫片保持分开。这些是短的杆状特征，大致平行于螺旋轴。我们已经将它们解释为附加的cl螺旋。通过对称性，每个鞭毛蛋白单体向内管贡献α-螺旋，向外管贡献两个α-螺旋，并且向间隔物贡献第四α-螺旋。我们已将外管中的一种类型的α-螺旋暂定为与鞭毛蛋白的30个C末端残基相似，而将其余三个α螺旋分配至类似的70个N末端残基。重建的这种解释与可用的生物化学，生物物理和氨基酸序列信息一致。我们还将介绍改进方法的详细信息，以提取和评估原始数据，以及评估三维地图中要素的统计意义。 [参考：49]

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