TMV is a rod-shaped virus of 3000 Å by 180 Å diameter. The central opening along the axis has a diameter of 40 Å. About 2130 identical protein subunits (Mr 17500) are arranged into a right-handed helix.
Th repeating basic unit consists of 49 subunits which cover a section of 69 Å of height in three turns of the helix (= a rise of 23 Å per turn). A single strand of RNA is placed between the protein subunits at a distance of 40 Å from the outer diameter. The figure to the left depicts one basic unit. Protein and RNA are shown in spacefill mode, RNA in white, the protein changing from red to blue along the helix. The uppermoust subunit is marked light brown. Each protein subunit covers three nucleotides of the RNA.
Further details will be shown with a single subunit.