Welsh L C, Marvin D A, Perham R N
Cambridge Centre for Molecular Recognition Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK.
J Mol Biol. 1998 Dec 18;284(5):1265-71. doi: 10.1006/jmbi.1998.2275.
X-ray fibre diffraction patterns of well-aligned Pf1 filamentous bacteriophage show sharp layer-lines attributable to an ordered helical array of protein subunits. Electron density maps calculated from the intensity on these layer-lines show no evidence for DNA following the symmetry of the protein, nor is there evidence on the diffraction patterns for the additional layer-lines expected if ordered DNA follows a symmetry different from that of the protein. We conclude that the interactions between DNA and protein in the Pf1 virion, like those in the Ff virion, are delocalized rather than specific, and the DNA structure in the virion is less regular than the protein structure. This conclusion has implications for the process of virion assembly, and we suggest a possible model for the change in the viral DNA symmetry as the DNA is passed to the virion from the intracellular complex with the viral gene 5 single-stranded DNA-binding protein.
排列良好的Pf1丝状噬菌体的X射线纤维衍射图谱显示出清晰的层线，这归因于蛋白质亚基的有序螺旋阵列。根据这些层线上的强度计算出的电子密度图没有显示出DNA遵循蛋白质对称性的证据，并且在衍射图谱上也没有证据表明如果有序DNA遵循与蛋白质不同的对称性会出现额外的层线。我们得出结论，Pf1病毒粒子中DNA与蛋白质之间的相互作用，就像Ff病毒粒子中的相互作用一样，是离域的而非特异性的，并且病毒粒子中的DNA结构比蛋白质结构更不规则。这一结论对病毒粒子组装过程具有启示意义，并且我们提出了一个可能的模型，用于解释当DNA从与病毒基因5单链DNA结合蛋白的细胞内复合物传递到病毒粒子时病毒DNA对称性的变化。
