title: Macromolecular structural transitions in Pf1 filamentous bacterial virus.
abstract: The filamentous bacterial virus Pf1 is a simple model for biological filaments. We have studied the structure of the virion and report here that the helix parameters of Pf1 change sharply with temperature at about 8 degrees C. Local interactions between protein subunits change by only a few tenths of an angstrom, but the changes are amplified between one end and the other of the virion to a rotation of 15 turns and a translation of 1,000 A. The limited nature of the phase transition is probably due to the constraints of 'knobs-into-holes' interaction between side chains of adjacent alpha-helical protein subunits. Treatment of the virion with ether causes a rearrangement of protein subunits into sheets, with the alpha-helices normal to the plane of the sheet. This phase transition suggests a model for virion assembly in the bacterial membrane.
mesh_terms: D001435:Bacteriophages / Q000648:ultrastructure*; D006860:Hydrogen Bonding; D008565:Membrane Proteins; D011485:Protein Binding; D011487:Protein Conformation; D014764:Viral Proteins; D014867:Water; D014961:X-Ray Diffraction
chemical_list: D008565:Membrane Proteins; D014764:Viral Proteins; D014867:Water