Scanning calorimetric studies of the stability of tobacco mosaic virus and aggregates of its coat protein

Abstract

The thermal denaturation of the common strain of a rod-shaped plant virus, tobacco mosaic virus, has been investigated by differential scanning calorimetry, and compared to that of various aggregation states of its coat protein and to that of three other TMV strains. The state of the virions was monitored by electron microscopy and analytical ultracentrifugation. The observed endotherms could be analysed in terms of a step-wise dissociation of the virions. The transition temperatures of the three successive structural changes increased with decreasing pH, from pH = 8.0 to pH = 5.0, although the corresponding enthalpy changes did not vary appreciably with pH. TMV-HR showed a stronger pH dependence of the transition temperatures than the other strains, probably reflecting the importance of the changes in affecting the charged amino acids of its coat protein. The first step of the dissociation, which correlates with the breaking up of the virions into three or four shorter rods, implies a conformational change of the particle that may be related to the first step of the in situ decapsidation of TMV.

A comparative differential scanning calorimetric study of tobacco mosaic virus and of its coat protein ts mutant

“…For both proteins this transition was irreversible and no additional peaks were observed on further heating up to 100°C. For UI CP our results agree with those of Mutombo et al [10].…”

“…Nevertheless, we estimated the areas under the peaks (AHc~0 and present them in Table 2. The values obtained are reproducible and agree rather closely with the analogous values reported by Mutombo et al [10]. (taking into account that these authors used a very large absorption coefficient of 3.28 optical units for intact viruses and due to this underestimated the virus concentration and overestimated the virus enthalpy values by about 40%).…”

“…The size of the small peak varied in different experiments and in all probability this peak corresponded to an admixture of either aberrant aggregates or of so-called stacked disks, while the major peak should correspond to normal RP. Similar DSC curves for U1 RP were obtained by Mutombo et al [10].…”

“…In the present work we have compared a stability of the wild-type (U1) and ts21-66 TMV virions and their CPs employing the method of differential scanning calorimetry (DSC). As far as we know, up to now only one DSC study of TMV virions and CP thermal denaturation has been published [10].…”

Polymorphism of turnip yellow mosaic virus empty shells and evidence for conformational changes occurring after release of the viral RNA

“…The transitions corresponded to dissociations or denaturations and they were always accompanied by partial aggregation. We know from our experiments on another plant virus, tobacco mosaic virus, that the aggregation of viral coat proteins is a significantly exothermic process [30]. We also know from our work on the swelling of isometric plant viruses that virions exhibit a considerable heterogeneity in their stability, although the transition is a highly cooperative process for each particle [31].…”