Interactions of mercuric chloride with turnip yellow mosaic virus: Dissociation of the virus and reassociation of the reaction products

Abstract

The action of HgCl 2 on turnip yellow mosaic virus (TYMV) has been investigated by analytical ultracentrifugation and electron microscopy, as well as by sucrose gradient analysis of 32P -or 35S-labeled virus. As increasing amounts of HgCl 2 (from r = 0.15 to r = 0.6, where r is the molar ratio of added HgCl 2 to nucleotide phosphorus) were added to TYMV, the virions were dissociated into RNA-free protein and a nucleoprotein containing an amount of protein increasing with r. At r > 0.9, Hg(II) bound to TYMV without disruption of the virion. These nucleoproteins were dissociated upon addition of mercaptoethanol. At r = 0.15, in the presence of chloride ions, Hg(II) bound only to the -SH groups of TMYV or artificial top component (ATC), leading to the total disruption of the protein shell. In the absence of chloride ions only a slight degradation was observed. When an adequate amount of HgCl 2 was added in two steps ( r = 0 → 0.45 → 0.9 or 1.5), the protein reassociated with the nucleoprotein moiety into particles which were less regular in shape and size than native TYMV. The nature of the forces stabilizing native and mercurated TYMV particles as well as ATC are discussed.