Pathways of degradation of brome mosaic virus particles as influenced by their RNA content

Abstract

The pathways of degradation of purified Brome Mosaic Virus (BMV) particles by increasing concentrations of CaCl 2 have been investigated as a function of time and pH. BMV was found to be stable at low pH even in the presence of high concentrations of CaCl 2, but degradation begins above a critical pH value (lower with increasing salt concentration). The nature of the degradation products depends on the CaCl 2 concentration. Between 0.1 and 0.5 M CaCl 2, BMV degrades into intact RNA, which precipitates as the Ca 2+ salt, and protein subunits. Above a critical concentration of CaCl 2, however, the release of the RNA is not accompanied by a collapse of the capsid but, rather, empty shells termed artificial top component (ATC) form. Polyacrylamide-gel analysis of the released RNA reveals that the various component particles of BMV exhibit a differential sensitivity towards dissociation by CaCl 2, and intermediates of degradation which had remained undetected in previous work were demonstrated.