Inactivation of the Yellow Strain of Cucumber Mosaic Virus by Pancreatic Ribonuclease

Abstract

The infectivity of cucumber mosaic virus Y strain (CMV-Y) decreased after mixing with bovine pancreatic ribonuclease (RNase). The amount of infectivity lost was dependent on the virus to enzyme ratio in the mixture and on the pH used for incubation. The enzyme seemed to bind at random to the surface of virus particles. Binding was partially reversed by pH adjustment. Most of the RNase which attached to the virus at pH 6 appeared to be released at pH 8. As the proportion of RNase in mixtures increased, the virus particles and enzyme formed complex aggregates. Degradation of virions occurred only at very high RNase concentrations. Degradation occurred more rapidly at pH 6 than pH 8. The infectivity loss upon addition of small amounts of RNase appeared not to be caused by aggregation or virion degradation. It is suggested that RNase attached to the virus prevents some processes necessary for initiation of infection or attacks the uncoated RNA.