Structure and Assembly of Helical Plant Viruses

利用本实验室已成功用于烟草花叶病毒(TMV)和TMV U2株系的纤维衍射方法，将以足以描述完整病毒的分子细节的分辨率确定一些螺旋植物病毒的结构。拟研究的病毒包括与TMV有远缘关系的病毒(黄瓜绿斑驳花叶病毒和黑麦草花叶病毒)，以及与之无关的斑点病毒木瓜花叶病毒(PMV)。分离的PMV外壳蛋白的结构将由结晶学确定。根据结构预测，TMV的突变体在组装或拆卸方面存在缺陷，将在这里设计并由合作者制造。通过电子显微镜和其他测量手段来研究它们的组装和拆解特性。将确定具有显著变化的组装性质的突变体的结构。这些杆状病毒是唯一一种使用X射线衍射法可以看到整个核酸基因组的病毒。对其结构的研究对于理解蛋白质-核酸相互作用以及生物系统中分子组装和识别过程具有重要意义。组装和识别是许多细胞过程中必不可少的步骤，在病毒感染和传播过程中也是如此。因此，这里提出的研究与多种具有医学和农业重要性的细胞系统相关。

The structures of a number of helical plant viruses will be determined at resolutions sufficient to describe the intact viruses in molecular detail, using the fiber diffraction methods already used successfully in this laboratory for tobacco mosaic virus (TMV) and the U2 strain of TMV. The viruses to be studied include viruses distantly related to TMV (cucumber green mottle mosaic virus and ribgrass mosaic virus), and the unrelated potexvirus papaya mosaic virus (PMV). The structure of the isolated coat protein of PMV will be determined crystallographically. Mutants of TMV, predicted from the structure to be deficient in assembly or disassembly, will be designed here and made by collaborators. Their assembly and disassembly properties will be studied here by electron microscopy and other measurements. Structures of mutants showing significantly changed assembly properties will be determined. %%% These rod-shaped viruses are the only viruses in which the entire nucleic acid genome can be seen using x-ray diffraction methods. Studies of their structures are important to understanding protein-nucleic acid interactions and the processes of molecular assembly and recognition in biological systems. Assembly and recognition are essential steps in many cellular processes, as well as in the processes of viral infection and propagation. The studies proposed here are therefore relevant to a wide variety of cellular systems of both medical and agricultural importance.