Studies on the interaction of p-chloromercuribenzoate with turnip yellow mosaic virus and with its artificial top component : I. Spectrophotometric measurement of the interaction and some properties of the reaction products

Abstract

The reaction of p-chloromercuribenzoate with turnip yellow mosaic virus and with its artificial top component (empty virus protein shella) has been studied by means of Boyer's spectrophotometric method. In the presence of 6 M urea or 1% sodium dodecyl sulfate, a direct titration could be performed with artificial top component. It was concluded that 645–660 moles of p-chloromercuribenzoate are bound by each particle of artificial top component. This figure has been confirmed by direct mercury determinations in the reaction product. Assuming that p-chloromercuribenzoate is bound by the sulfhydryl groups of the protein, the cysteine content (on a basis of grams cysteine/ 100 g. protein) was calculated to be about 2.26%. This is in reasonable agreement with the values of 2.35 and 2.5% obtained from the amino acid analysis reported in the literature. The reaction of the virus, as well as of its artificial top component with p-chloromercuribenzoate, is accompanied by a degradation of the protein shell into structurally different material, which is probably smaller in size. In the reaction with virus, ribonucleic acid is liberated simultaneously. The possible implications of this interaction with p-chloromercuribenzoate for the tertiary structure of the virus have been discussed.