The relationship between the components of cowpea mosaic virus: I. Two ribonucleoprotein particles necessary for the infectivity of CPMV

Abstract

Plants infected with cowpea mosaic virus produce two nucleoprotein components with 23% and 32% ribonucleic acid, respectively. The components were separated by zonal density gradient centrifugation in a sucrose density gradient in a B IV zonal rotor of Spinco, and further purified by repeated zonal density gradient centrifugation or by equilibrium density gradient centrifugation in CsCl. Prolonged purification of the components leads to loss of the infectivity, which can be restored by mixing of the two components. The infectivity of a mixture depends upon the proportion of the two components and the concentration of the component present in the lowest amount. It is concluded that the separate components are noninfectious and that the infectivity of cowpea mosaic virus depends upon the presence of both components.