RESTRICTED REACTIVITY OF EPSILON-AMINO GROUPS OF TOBACCO MOSAIC VIRUS PROTEIN TOWARD TRINITROBENZENESULFONIC ACID

The reactivity of the ɛ-amino groups of tobacco mosaic virus protein was investigated with trinitrobenzenesulfonic acid, a reagent specific for primary amines. The kinetics of trinitrophenylation was followed spectrophotometrically at room temperature in the pH range from 7.5 to 10.4. The half-times of the trinitrobenzenesulfonic acid reaction with tobacco mosaic virus protein were compared with the half-times of the trinitrobenzenesulfonic acid reaction with bovine serum albumin, poly-L-lysine, and denatured (performic acid oxidized) tobacco mosaic virus protein, under identical conditions. Trinitrophenylation of tobacco mosaic virus protein was found to proceed many times more slowly than the reaction of trinitrobenzenesulfonic acid with the other materials. At pH 7.5 tobacco mosaic virus protein did not react at all with the trinitrobenzenesulfonic acid, while the other materials did react. The reaction proceeds to completion at the higher pH values but denatures the tobacco mosaic virus protein. Whole virus did not react with trinitrobenzenesulfonic acid at pH 8.6. A model involving two proton-sharing associations between lysine and tyrosine side chains is proposed to explain these observations and several anomalies of the chemistry of the ɛ-amino groups of tobacco mosaic virus protein previously reported in the literature. © 1969, American Chemical Society. All rights reserved.