Filamentous bacterial viruses.
D A Marvin,Barbara Hohn +1 more
469
TL;DR: X-ray fibre diffraction patterns of the Pf 1 species of virus at 4°C, oriented in a strong magnetic field, give three-dimensional data to 4 A resolution, and an electron density map calculated from native virus and a single iodine derivative, shows a helix pitch of 5.9 A.
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Abstract: The filamentous bacterial virus is a simple and well-characterized model system for studying how genetic information is transformed into molecular machines. The viral DNA is a single-stranded circle coding for about 10 proteins. The major viral coat protein is largely α-helical, with about 46 amino acid residues. Several thousand identical copies of this protein in a helical array form a hollow cylindrical tube 1–2μ long, of outer diameter 60 A and inner diameter 20 A, with the twisted circular DNA extending down the core of the tube. Before assembly, the viral coat protein spans the cell membrane, and assembly involves extrusion of the coat from the membrane. X-ray fibre diffraction patterns of the Pf 1 species of virus at 4°C, oriented in a strong magnetic field, give three-dimensional data to 4 A resolution. An electron density map calculated from native virus and a single iodine derivative, using the maximum entropy technique, shows a helix pitch of 5.9 A. This may indicate a stretched A-helix, or it may indicate a partially 310 helix conformation, resulting from the fact that the coat protein is an integral membrane protein before assembly, and is still in the hydrophobic environment of other coat proteins after assembly.
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Citations
Single-stranded DNA binding and methylation by EcoP1I DNA methyltransferase
TL;DR: In vitro methylation of single-stranded DNA by the type III methyltransferase EcoP1I is described to allow understanding of the mechanism of action of these enzymes and also their role in the biology of single -stranded phages.
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In Vitro Studies of Photochemically Cross-Linked Protein-Nucleic Acid Complexes. Determination of Cross-Linked Regions and Structural Relationships in Specific Complexes
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TL;DR: It is desirable to understand how specificity is achieved and to determine what factors are responsible for the strength of specific protein-nucleic acid associations.
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Structure of Viral Nucleic Acids in Situ
T. I. Tikchonenko
- 01 Jan 1975
TL;DR: The main principles of the structural organization of nucleic acids in solution having been established, scientists are increasingly turning their attention to the fine features of the secondary structure of DNA and RNA and the possibilities of their reversible conformational alterations under the influence of various external factors as discussed by the authors.
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Maximum Entropy in Structural Molecular Biology: The Fiber Diffraction Phase Problem
Richard K. Bryan
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TL;DR: In this paper, the maximum entropy method of image processing is applied to the problem of calculating a map of electron density from its x-ray fiber diffraction pattern, which is illustrated by application to the filamentous bacterial virus Pf1.
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