title: Structure of EDTA-treated satellite tobacco necrosis virus at pH 6.5.
abstract: The crystal structure of EDTA-treated satellite tobacco necrosis virus (STNV) at pH 6.5 has been determined to 7.5 A resolution (1 A = 0.1 nm) with molecular replacement techniques, using the known structure of the protein subunit. The calcium ions at the 3-fold contacts are absent, whereas the calcium ions on the 5-fold axes still remain. The protein shell is slightly expanded. The expansion does not impose any large conformational changes on the subunits and the subunit contacts are to a large extent retained. The electron density map shows high levels of density in the RNA region. It is found close to the protein shell but well-separated from the protein. This density indicates a preferential ordering of the RNA in certain regions, but does not allow a detailed interpretation of the RNA conformation. A similar density in the RNA region is also found in a low resolution map of native STNV.
mesh_terms: D004492:Edetic Acid / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D010942:Plant Viruses / Q000187:drug effects / Q000648:ultrastructure*; D010947:Plants, Toxic; D012367:RNA, Viral; D014026:Nicotiana; D014764:Viral Proteins; D014961:X-Ray Diffraction
chemical_list: D046911:Macromolecular Substances; D012367:RNA, Viral; D014764:Viral Proteins; D004492:Edetic Acid