Index >> Virus Structure and Classification >> Tobacco Mosaic Virus - TMV

Tobacco Mosaic Virus - TMV
In 1936 Stanley isolated the tobacco mosaic virus in crystalline state from the sap of infected tobacco plants.

Since then much work has been done to elucidate the structure of the TMV. The virus is rod shaped, about 300nm long and 15-18 nm in diameter.

X-ray diffraction studies have shown that the virus consists of a protein tube with a lumen of 2oA enclosing a single strand of helically coiled RNA. The tube is made up of a number of identical subunits (monomers) of protein arranged in a helical manner.

The RNA is a single stranded molecule coiled into a helix BOA in diameter. It follows the pitch of the protein helix. Each turn of the RNA helix contains about 49 nucleotides, and has a pitch of 23°. The RNA is infective by itself, although much less so than the intact virus.

This is because unprotected RNA is subjected to the action of enzymes (nucleases), and is thus destroyed. The protein functions as a protective tube around the RNA.