This family contains coat proteins from tobamoviruses, which are ssRNA positive-strand viruses with no DNA stage. Examples include Tobacco mosaic virus (TMV), Cucumber green mottle mosaic virus and Ribgrass mosaic virus (RMV).
In order to establish infections, viruses must be delivered to the cells of potential hosts and must then engage in activities that enable their genomes to be expressed and replicated. With most viruses, the events that precede the onset of production of progeny virus particles are referred to as the early events and, in the case of positive-strand RNA viruses, they include the initial interaction with and entry of host cells and the release (uncoating) of the genome from the virus particles. The uncoating process in TMV may involve the bidirectional release of coat protein subunits from the viral RNA which may be mediated by cotranslational and coreplicational disassembly mechanisms .
The TMV particle is assembled from its constituent coat protein and RNA by a complex process. The protein forms an obligatory intermediate (a cylindrical disk composed of two layers of protein units), which recognises a specific RNA hairpin sequence. This mechanism simultaneously fulfils the physical requirement for nucleating the growth of the helical particle and the biological requirement for specific recognition of the viral DNA .