Quantized incorporation of RNA during assembly of tobacco mosaic virus from protein disks

Reassembly of tobacco mosaic virus from the isolated RNA and protein, supplied as a disk preparation consisting of over 75% as the disk aggregate, has been followed by the protection of the RNA from nuclease digestion. The sizes of the RNA fragments were determined on agarose/acrylamide gels.During the first few minutes the protected RNA is found to be “quantized” into discrete lengths, differing on average by about 50 or 100 nucleotides, corresponding to one or two turns of the virus helix and strongly supporting the hypothesis that elongation in the major direction, towards the 5′-hydroxyl end, is occurring by the direct addition of protein disks. Protected RNA of the full length found in tobacco mosaic virus is visible within six minutes of starting reassembly, and by 30 minutes most of the RNA is fully protected.