Wikoff W R, Tsai C J, Wang G, Baker T S, Johnson J E
Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Virology. 1997 May 26;232(1):91-7. doi: 10.1006/viro.1997.8543.
The three-dimensional structure of cucumber mosaic virus (CMV) was analyzed at 23 A resolution by cryoelectron microscopy and image reconstruction, demonstrating structural similarity to cowpea chlorotic mottle virus (CCMV), another member of the Bromoviridae family. The CMV structure was determined at 8 A resolution by X-ray crystallography with phases determined by single isomorphous replacement and refined by fivefold noncrystallographic symmetry averaging. The X-ray structure agreed with the electron microscopy reconstruction; the electron density is consistent with beta-barrel subunits arranged with T = 3 quasi-symmetry in an orientation similar to that observed in CCMV. Strong density surrounding the icosahedral threefold axes (quasi sixfold axes in the T = 3 particle) between 80 and 100 A from the particle center formed a cylinder of radius 11 A, similar to the density observed in the same region of CCMV. This density corresponds to the beta-annulus of CCMV, which differentiates hexamers from pentamers and determines the formation of the T = 3 particles. The CMV and CCMV amino acid sequences were aligned, providing information (based on the CCMV atomic model) about the probable distribution of residues in the three-dimensional structure of CMV.
通过冷冻电子显微镜和图像重建技术，以23埃的分辨率分析了黄瓜花叶病毒（CMV）的三维结构，结果表明其与豇豆花叶病毒（CCMV）（雀麦花叶病毒科的另一个成员）在结构上具有相似性。通过X射线晶体学以8埃的分辨率确定了CMV的结构，其相位通过单同晶置换法确定，并通过五重非晶体学对称平均法进行了优化。X射线结构与电子显微镜重建结果一致；电子密度与以T = 3准对称排列的β-桶状亚基一致，其取向与在CCMV中观察到的相似。在距粒子中心80至100埃的二十面体三重轴（T = 3粒子中的准六重轴）周围有很强的密度，形成了一个半径为11埃的圆柱体，类似于在CCMV相同区域观察到的密度。这种密度对应于CCMV的β-环，它区分六聚体和五聚体，并决定了T = 3粒子的形成。对CMV和CCMV的氨基酸序列进行了比对，提供了（基于CCMV原子模型）关于CMV三维结构中残基可能分布的信息。
