Purification and properties of the pea enation mosaic virus.

A procedure was developed for the purification of the pea enation mosaic virus (PEMV) using differential and rate zonal centrifugation in sucrose density gradients. Infectivity and serological data indicated that the highest virus concentration occurs in infected peas (Pisum sativum) 10-12 days after mechanical inoculation when the plants are grown at 16-22 degrees . Tests with several buffer salts at various concentrations and pH values showed that 0.1-0.3 M acetate, pH 6.0, was the most suitable for extraction of virus and maintaining its infectivity. Approximately 0.3 mg of virus could be obtained per gram of infected plant material. Infectivity was found to be associated with two nucleoprotein components with sedimentation coefficients of 106 +/- 2 and 122 +/- 1.5 S, which separated during density gradient centrifugation but which were not present in similarly treated healthy tissue. The slower sedimenting component appeared to be more infectious than the bulk of the virus material, which sedimented somewhat more rapidly. Both components were composed of small polyhedral particles approximately 36 micron in diameter as revealed by electron microscopy. In addition to the two infectious components, one other which was antigenically incomplete and of low molecular weight occurs in freshly extracted sap and the supernatant of ultracentrifuged homogenates of infected peas.