Studies on the interaction of p-chloromercuribenzoate with turnip yellow mosaic virus and with its artificial top component. II. Interrelationships of the interaction and structural changes

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The interaction of p-chloromercuribenzoate with the —SH groups of turnip yellow mosaic virus and of its empty protein shell (artificial top component) leads to a destruction of the rigid structure of these particles. The structural change occurring in the empty protein shells has been analyzed in conjunction with the reaction of —SH and p-chloromercuribenzoate. Use was made of cysteine to inhibit the interaction at different time intervals. The extent of structural change was estimated by nitrogen determinations in the reaction products that had been fractionated by an acid-precipitation method. The reaction of —SH with the mercurial was followed by spectro-photometry. It could be demonstrated that considerable reaction with p-chloromercuribenzoate may take place before there is destruction of the structure of artificial top component. In accordance with an earlier hypothesis of Boyer, the partially mercuribenzoate-substituted particles are less stable, although crystals can still be obtained from their purified suspensions. Once structural change has been induced in artificial top component, the experimental data indicate a liberation of previously “masked” —SH groups which then react rapidly with p-chloromercuribenzoate. The implications of the above findings are discussed.