The reversible reaction of brome grass mosaic virus and its RNA with mercuric ions

Abstract

Hg 2+ reacts with the RNA isolated from brome grass mosaic virus (BMV), and also with BMV itself without degradation of the virus particle. In both reactions, the addition of HgCl 2 causes a shift of the ultraviolet spectrum toward longer wavelengths, and the spectral curves display two isosbestic points in the same range of r a ( r a is the number of moles of Hg (II) added per mole of phosphorus). These two isosbestic points indicate the formation of two successive mercury complexes. This was confirmed by direct determination of the amounts of Hg(II) bound per mole of phosphorus to BMV and isolated BMV RNA ( r b ). The sedimentation coefficient of BMV increases markedly upon addition of HgCl 2. Up to r b = 0.80 , this increase is due to the increase of the molecular weight of the BMV particle upon mercury binding, without configurational change of the particle. Above r b = 0.80 , a slight shrinkage of the particle occurs. The infectivity of both RNA and virus decreases linearly with the amounts of mercury bound. All the modifications in the biological and physiochemical properties of virus and RNA can be easily reversed by strong complexing reagents of Hg(II), such as EDTA, mercaptoethanol and CN −. From our results, we have drawn some conclusions about the configuration and the localization of the RNA in situ, and about the RNA-protein interactions in BMV.