STUDIES ON INTERACTION OF P-MERCURIBENZOATE WITH TURNIP YELLOW MOSAIC VIRUS .V. INDUCED RIBONUCLEASE SENSITIVITY AND DEGRADATION OF VIRION

Fully pMB-substituted preparations derived from TYMV purified in the presence of bentonite (B-TYMV) were more infectious than those of TYMV purified with the butanol-chloroform method (BC-TYMV). This infectivity difference was also reflected in the physical integrity of the respective constituent RNA's, and in the possibility of releasing physically intact RNA from pMB-B-TYMV by means of buffer treatment at neutral pH in the cold. This observation combined with a knowledge of the pMB-induced change in capsid conformation, led to the experimental inactivation and degradation of pMB-TYMV with pancreatic ribonuclease. At concentrations of 10-100 μg/ml, pMB-TYMV was almost completely inactivated after incubation for 45 minutes at 0° with ribonuclease at 10-2 μg/ml. Similar concentrations of untreated TYMV were not affected when incubated under the same conditions with ribonuclease at 1.0 μg/ml. The ribonuclease inactivation of pMB-TYMV followed first-order kinetics. Comparison with the ribonuclease inactivation of equivalent amounts of isolated TYMV-RNA, suggested that the modified capsid afforded the RNA some residual shielding. Extensive hydrolysis of the RNA inside the modified virus led to the release of RNA fragments, and to collapse of the capsid structure. The possible significance of these, and analogous findings with other viruses, is discussed. © 1968.