Changes in the organization of bromegrass mosaic virus in response to cation binding as probed by changes in susceptibility to degradative enzymes

The swelling at alkaline pH and the sensitivity of bromegrass mosaic virus to degradative enzymes are less in the presence of moderate concentrations of KC1 than at low salt concentration. The virus can be efficiently stabilized above neutral pH by divalent metal cations, especially Ca2+, but this effect is antagonized by KC1. Polyamines also can stabilize the virus, but the salt concentrations for optimal protection of the viral RNA and protein moieties are then different, as judged by their susceptibility to degradative enzymes. These changes in the structural organization of the virus revealed by proteases and pancreatic ribonuclease as accessibility probes complement the data from neutron-scattering studies. On the basis of these studies, a tentative model is proposed to account for the polymorphism of BMV in various ionic environments.