Tobacco mosaic virus particle structure and the initiation of disassembly

The structure of an intact tobacco mosaic virus (TMV) particle was determin ed at 2.9 Angstrom resolution using fibre diffraction methods. All residues of the coat protein and the three nucleotides of RNA that are bound to eac h protein subunit were visible in the electron density map. Examination of the structures of TMV, cucumber green mottle mosaic virus and ribgrass mosa ic virus, and site-directed mutagenesis experiments in which carboxylate gr oups were changed to the corresponding amides, showed that initial stages o f disassembly are driven by complex electrostatic interactions involving at least seven carboxylate side-chains and a phosphate group. The locations o f these interactions can drift during evolution, allowing the viruses to ev ade plant defensive responses that depend on recognition of the viral coat protein surface.