Projection structure of VP6, the rotavirus inner capsid protein, and comparison with bluetongue VP7.
Projection structure of VP6, the rotavirus inner capsid protein, and comparison with bluetongue VP7.
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DOI：
10.1006/jmbi.1997.1179
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发表时间：
1997-09
影响因子：
5.6
通讯作者：
G. G. Hsu-G.;A. Bellamy;M. Yeager
中科院分区：
文献类型：
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作者：
G. G. Hsu-G.;A. Bellamy;M. Yeager
轮状病毒核衣壳蛋白（VP 6）是内衣壳颗粒（ICP）的主要结构蛋白。VP 6是RNA转录所必需的，并与轮状病毒装配途径中涉及的病毒编码的糖蛋白受体（NSP 4）结合。为了探索VP 6的结构，产生了VP 6的二维（2D）晶体，并通过电子显微镜和图像处理进行了检查。从负染色的2D VP 6晶体的低剂量图像计算的傅立叶变换显示了p6平面群对称性的13 A分辨率的完整数据。为了校正源自电子显微镜图像的振幅的分辨率依赖性下降，通过应用约360 A-2的B因子，将轮状病毒VP 6振幅缩放至源自原子模型的蓝舌病VP 7振幅。晶胞（a=B=101（+/-2）A，γ =120（+/-1）度）含有两个VP 6三聚体，每个三聚体由三个直径约30 A的大致圆形亚基组成。当在25至40 A分辨率下组装在T= 131二十面体内衣壳颗粒中时，VP 6的三聚体组织类似于VP 6的寡聚体结构。然而，三聚体中心的通道在我们的图中以15 A分辨率更好地分辨。将轮状病毒VP 6的投影结构与蓝舌病毒的同源蛋白（VP 7）进行了比较，蓝舌病毒也是呼肠孤病毒科的成员。值得注意的是，VP 6和蓝舌病VP 7在内衣壳表面组装为260个衣壳。为了比较VP 6和VP 7，使用由X射线晶体学导出的原子模型生成分辨率为15 A的蓝舌病VP 7的投影图。VP 6和VP 7均表现出具有中央通道的三聚体组织，尽管45 kDa VP 6和38 kDa VP 7一级序列之间的比对同一性仅为12%。VP 6形成良好有序的2D晶体的能力应该能够通过冷冻电子显微镜进行更高分辨率的结构分析，这将扩展我们对二十面体ICP结构的理解，澄清VP 6与NSP 4受体相互作用的机制，并允许更详细地比较VP 6和VP 7。
The rotavirus nucleocapsid protein (VP6) is the major structural protein of inner capsid particles (ICP). VP6 is essential for RNA transcription and binds to a virally encoded glycoprotein receptor (NSP4) involved in the rotavirus assembly pathway. To explore the structure of VP6, two-dimensional (2D) crystals of VP6 were generated and examined by electron microscopy and image processing. Fourier transforms computed from low-dose images of negatively stained 2D VP6 crystals displayed complete data to 13 A resolution for p6 plane group symmetry. To correct for the resolution dependent fall-off of the amplitudes derived from electron microscopic images, the rotavirus VP6 amplitudes were scaled to the bluetongue VP7 amplitudes derived from the atomic model by applying a B factor of -360 A-2. The unit cell (a=b=101(+/-2)A, gamma=120(+/-1) degrees) contains two VP6 trimers, each composed of three roughly circular subunits approximately 30 A in diameter. The trimeric organization of VP6 is similar to the oligomeric structure of VP6 when assembled in T=13l icosahedral inner capsid particles at 25 to 40 A resolution. However, a channel at the center of the trimer is better resolved in our map at 15 A resolution. The projection structure of rotavirus VP6 was compared to the homologous protein (VP7) of bluetongue virus, which is also a member of the family of Reoviridae. Notably, both VP6 and bluetongue VP7 assemble as 260 capsomers on the surface of the inner capsid. To compare VP6 and VP7, a projection map of bluetongue VP7 at 15 A resolution was generated using the atomic model derived by X-ray crystallography. VP6 and VP7 both exhibit a trimeric organization with a central channel, even though the alignment identity between the 45 kDa VP6 and the 38 kDa VP7 primary sequences is only 12%. The ability of VP6 to form well-ordered 2D crystals should enable a higher resolution structure analysis by cryo-electron microscopy that will extend our understanding of the icosahedral ICP structure, clarify the mechanism by which VP6 interacts with the NSP4 receptor, and allow a more detailed comparison of VP6 and VP7.