FURTHER-STUDIES ON RNA COMPONENT DISTRIBUTION AMONG NUCLEOPROTEINS OF CUCUMBER MOSAIC-VIRUS

Several attempts to obtain a more reliable definition of the RNA component distribution among the nucleoproteins of cucumber mosaic virus (CMV) are described. Preparative isopycnic centrifugation of formaldehyde-stabilized CMV could not be applied because CMV component cross-linking precluded its further dissociation by SDS [sodium dodecyl sulfate] or Pronase for RNA component analysis. In salt stability tests, preparations of CMV-D were incompletely degraded in 2 M RbCl and the undegraded virus had the same RNA component ratio as untreated CMV-D. The undegraded CMV-D was fractionated following isopycnic centrifugation in RbCl on a preparative scale. RNA 1 (1.07 .times. 106 daltons) was found predominantly in the heavy nucleoprotein fractions, and RNA 2 (0.95 .times. 106 daltons) in the light ones. RNA 3 (0.69 106 daltons) and RNA 4 (0.33 .times. 106 daltons) were found in slightly larger proportions in the middle density fractions. RNA 5 (about 0.1 .times. 106 daltons) was almost evenly distributed among all nucleoprotein fractions. In CMV-D, with its RNA components basically distributed like brome mosaic virus, there are probably other types of nucleoproteins which have RNA 2 and RNA 3 combined with RNA 5, or RNA 5 molecules without the other components.