Über die Bedeutung der Aminogruppen für die Vermehrungsfähigkeit des Tabakmosaikvirus

Abstract

70% of the free amino groups of the tobacco-mosaic virus (TM virus) can be acetylated with ketene, or 43-63% can be altered with phenylisocyanate without changing the propagation capacity of the virus. The greater part of the free amino groups are therefore not necessary for reproduction of the virus. The virus has an amino N content of about 0.25% (0.018 mol. NH2 per 100 gm. of virus). A highly acetylated TM virus derivative, which contains only 1% of the original biological activity, is warmed for 60 min. at 35[degree] in buffer solns. of pH 9, 10 and 11. Control solns. of unacetylated virus are treated in the same manner. When tested on tobacco plants, the activity of both solns. remains unchanged at pH 9 and 10, but is destroyed at pH 11. Inactivation of the virus by long continued acetylation is probably due to esterification of difficultly saponifiable hydroxyl or amino groups together with the tryosine residues. Tobacco plants are infected with a highly acetylated TM virus which contains no free virus. After 4 weeks, the virus protein produced is purified and found to be normal TM virus. Since the plants do not seem to contain an enzyme capable of splitting off the acetyl groups, the acetylated virus must have been capable of propagating itself. When 300 mg. of TM virus are treated with 60 mg. p-bromophenylisocyanate, a product having all the enzyme activity, and containing 0.58% Br and 0.004 mol. isocyanate per 100 gm. of virus is obtained. Deamination of TM virus with Na nitrite is associated with loss of virus activity.