Properties of turnip yellow mosaic virus in cesium chloride solutions: the formation of high-density components.
The bottom component B1a of TYMV with a buoyant density of 1.42-1.43 g/ml, is converted to a more dense particle B2a following CsCI density gradient centrifugation. This conversion is complete after a prior incubation of the virus in the CsCl solution at elevated temperatures. It is shown that the formation of B28 is accompanied with a loss from the virion of polyvalent cations like spermidine and Mg2+. The exchange of the latter ions for Cs ions is responsible for the occurrence of the higher-density particles. The more dense component B2a can be converted back to B,; like particles upon incubation in the presence of 0.1 M M9Cl2. If TYMV or component B1a is centrifuged in the presence of Mg2+, the conversion into B2a is prevented. The latter phenomenon allowed the isolation and characterization of the minor components B1b and B1c, previously postulated (Mellema et al. (1979), Virology 96, 38-46). The phenomenon of conversion appeared to be restricted to the components of the B series of TYMV; indicating that the class of light minor components does not contain artefacts of the CsCl gradient centrifugation. The formation of B2a is accompanied by degradation of RNA, which might be due to some conformational change in the virion, rendering the RNA vulnerable to RNases.
Noort
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Department of Biochemistry, State University of Leiden, P.O. Box 9505, 2300 RA Leiden, The Netherlands.
van den Dries
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Pleij
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Jaspars
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Bosch
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