title: Structure of the protein and DNA in fd filamentous bacterial virus.
abstract: The virion of filamentous bacterial viruses comprises a cylindrical protein shell of o.d. approximately 60 A and i.d. 20A, 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 membrane. Studies of the virion by X-ray fibre diffraction show that the protein coat consists largely of alpha-helices oriented roughly parallel to the axis of the virion. 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 magnet. 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).
mesh_terms: D001435:Bacteriophages / Q000648:ultrastructure*; D002213:Capsid; D004279:DNA, Viral; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D011487:Protein Conformation; D014764:Viral Proteins; D014961:X-Ray Diffraction
chemical_list: D004279:DNA, Viral; D014764:Viral Proteins