Conformational features of cowpea chlorotic mottle virus RNA and the stability of the virus

Physico chemical properties of the RNA of cowpea chlorotic mottle virus (CCMV), either as extracted from or contained in virus particles, were investigated. The similarity of the hypochromicity obtained on alkali hydrolysis of isolated CCMV RNA and that of RNA in virus particles showed that the secondary structure could be conserved upon extracting the RNA from virus particles. Through the pH range in which the virus particles swell, the hypochromicity determined from the melting profiles of purified, unfractionated CCMV RNA remained constant, as did the sedimentation coefficients of the separated RNA species which comprise the multicomponent genome of CCMV. Changes in RNA conformation are, therefore, probably not responsible for the swelling of the virus particles.