The self-assembly of tobacco mosaic virus: influence of the viral RNA and protein components upon the assembly process.

The initial stage in the self-assembly of tobacco mosaic virus (TMV) RNA and coat protein into virions involves insertion of a loop of TMV RNA between layers of a double-layered disk of TMV protein (containing 17 coat protein subunits per layer) via the central channel of the disk, followed by conversion of the disk-RNA complex into a two-turn protohelix and addition of more protein (elongation). This mechanism leads to assembling particles in which one of the uncoated RNA tails, that containing the 5'-terminus, runs back along the central channel of the growing rod.