Structure of the protein and DNA in fd filamentous bacterial virus
Structure of the protein and DNA in fd filamentous bacterial virus
复制标题
fd丝状细菌病毒蛋白质和DNA的结构
作者：
D. Banner;C. Nave;D. Marvin
丝状细菌病毒的病毒颗粒包含一个圆柱形的蛋白质外壳。 ∼60 Å 和内径20 Å，包含一个单链环状 DNA 分子，该分子具有两条方向相反但不碱基配对的链，延伸至病毒粒子的长度。病毒体的组装涉及到 DNA 与病毒 DNA 结合蛋白在细胞内的预包装，然后当生长的病毒体穿过细菌膜时，该蛋白被外壳蛋白取代。通过 X 射线纤维衍射对病毒体的研究表明，蛋白质外壳主要由大致平行于病毒体轴的 α 螺旋组成2,3。由于平面肽的法线往往与磁场法线对齐，因此可以使用强磁铁显着改善纤维中病毒粒子的方向4,5。这项技术在 Pf1 病毒株上的成功使我们将其应用于更知名的 fd (f1, M13) 病毒株。我们在这里报告了从改进的衍射图样中获得的有关 fd 病毒粒子中蛋白质和 DNA 排列的新信息（图 1）。
The virion of filamentous bacterial viruses comprises a cylindrical protein shell of o.d. ∼60 Å and i.d. 20 Å, containing a single-stranded circular DNA molecule which has two oppositely directed but not base-paired strands extending the length of the virion. The assembly of the virion involves an intracellular prepackaging of the DNA with a viral DNA-binding protein which is then displaced by the coat protein as the growing virion crosses the bacterial membrane1. Studies of the virion by X-ray fibre diffraction show that the protein coat consists largely of α-helices oriented roughly parallel to the axis of the virion2,3. As the normal to a planar peptide tends to align normal to a magnetic field, it is possible to improve significantly the orientation of virions in fibres using a strong magnet4,5. The success of this technique with the Pf1 strain of virus led us to apply it to the better-known fd (f1, M13) strain. We report here new information about the arrangement of protein and DNA in the fd virion obtained from the improved diffraction pattern (Fig. 1).