RNA : protein and protein : Protein interactions in the virions of southern bean mosaic virus : (isometric plant viruses, stabilizing interactions, capsid structure)

Virions of southern bean mosaic virus (SBMV), a small RNA-containing isometric plant virus, are stabilized with strong linkages between the coat protein subunits mediated through divalent metal ions (magnesium, calcium) and hydrophobic interactions. Virion treatments interfering with these inter-subunit linkages markedly alter the conformation and stability of the SBMV capsid. The virion capsid is composed of the entire complement of the viral protein, including a small proportion of stable coat protein dimers formed with covalent linkages between the epsilon-amino groups of the lysyl residues. The viral RNA is located within the capsid but 'loosely' contacts only one-third of the total coat protein. A tentative structural model of SBMV virions based upon physico-chemical and morphological considerations is proposed.O. P. SEHGAL and C.H. HSU, Department of Plant Pathology, University of Missouri, Columbia, MO