Maximum-entropy calculation of the electron density at 4 A resolution of Pf1 filamentous bacteriophage.
A 4 A electron-density map of Pf1 filamentous bacterial virus has been calculated from x-ray fiber diffraction data by using the maximum-entropy method. This method produces a map that is free of features due to noise in the data and enables incomplete isomorphous-derivative phase information to be supplemented by information about the nature of the solution. The map shows gently curved (banana-shaped) rods of density about 70 A long, oriented roughly parallel to the virion axis but slewing by about 1/6th turn while running from a radius of 28 A to one of 13 A. Within these rods, there is a helical periodicity with a pitch of 5 to 6 A. We interpret these rods to be the helical subunits of the virion. The position of strongly diffracted intensity on the x-ray fiber pattern shows that the basic helix of the virion is right handed and that neighboring nearly parallel protein helices cross one another in an unusual negative sense.
D001435:Bacteriophages / Q000648:ultrastructure*; D004279:DNA, Viral / Q000032:analysis; D008433:Mathematics; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D011550:Pseudomonas aeruginosa / Q000648:ultrastructure; D013816:Thermodynamics; D014764:Viral Proteins / Q000032:analysis; D014771:Virion / Q000648:ultrastructure; D014961:X-Ray Diffraction
D004279:DNA, Viral; D014764:Viral Proteins