Dimethyl Sulphoxide (DMSO) Disassembles Tobacco Mosaic Virus Predominantly from the 5'-end of the Viral RNA

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Abstract
Summary The effect of dimethyl sulphoxide (DMSO) on the stability of native and EDTA-treated tobacco mosaic virus (TMV, Vulgare strain) has been reinvestigated using a variety of chemical and biochemical techniques. Contrary to earlier reports, we conclude that TMV rods behave as a heterodisperse population, exhibiting one of two modes of uncoating. More than 50% of the rods disassemble rapidly and extensively in a unique polar fashion beginning at the 5′-end of the viral RNA. The remainder of the rod population uncoats more slowly, less extensively, and exhibits substantial bidirectional exposure of the viral RNA, commencing at the 3′-terminus but proceeding for no more than 500 nucleotides before the major uncoating event again shifts to the 5′-ends of the particles. A portion of the coat protein gene and the region around the assembly initiation site on the viral RNA appears most resistant to uni- or bidirectional stripping; this is in contrast to previous reports. This complex, biphasic behaviour of the TMV rod population, which produces two broad and relatively ill-defined peaks of metastable nucleoprotein intermediates, may account for many of the inconsistencies prevalent in earlier work.