Monopartite Spherical Viruses
Southern bean mosaic virus (SBMV) is the archetype of group sobemovirus, which also includes turnip rosette virus (TRoSV), cocksfoot mottle virus, rice yellow mottle virus, and sowbane mosaic virus. SBMV, a pathogen of cultivated legumes, is widespread in the tropical and warm temperate parts of the world. SBMV virions are punned by precipitation with 4 to 8% polyethylene glycol, acid clarification, and differential centrifugation. SBMV virions are spheroidal. By electron microscopy they measure 30 nm in diameter, a value which agrees with the data obtained from X-ray diffraction and neutron scattering studies. SBMV interacts strongly with a lipid composite of phosphatidylcholine, cholesterol, and stearylamine, which forms a uniform 5-nm thick shell around the individual virions. Native SBMV is stable in the presence of protein denaturants and enzymes, indicating a highly integrated and coordinated macromolecular organization.