Properties of the Coat Protein of a New Tobacco Mosaic Virus Coat Protein ts-Mutant

Abstract

Amino acid substitutions in a majority of tobacco mosaic virus (TMV) coat protein (CP) ts-mutants have previously been mapped to the same region of the CP molecule tertiary structure, located at a distance of about 70 A from TMV virion axis. In the present work some properties of a new TMV CP ts-mutant ts21-66 (two substitutions I21=>T and D66=>G, both in the 70-A region) were studied. Thermal inactivation characteristics, sedimentation properties, circular dichroism spectra, and modification by a lysine-specific reagent, trinitrobenzensulfonic acid, of ts21-66 CP were compared with those of wild-type (U1) TMV CP. It is concluded that the 70-A region represents the most labile portion of the TMV CP molecule. Partial disordering of this region in the mutant CP at permissive temperatures leads to loss of the capacity to form two-layer aggregates of the cylindrical type, while further disordering induced by mild heating results also in the loss of the ability to form ordered helical aggregates.

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

“…As was mentioned in Section l, at pH 8.0 and low ionic strength TMV CP exists in the form of small (3 or 4S) Aprotein aggregates (see also Table 1). Previously we reported that ts21-66 CP in the form of the A-protein by several criteria displays a somewhat lower thermostability than wildtype (U l) CP [9] and behaves in this respect like CPs of the other mutants of this type [13,14]. This conclusion was confirmed by the results of DSC experiments.…”

“…A large size of the heat absorption peak at 38 or 41°C and an absence of additional peaks at higher temperatures testify against our previous suggestion [9], that only partial denaturation of U1 and ts21-66 CPs takes place at these low temperatures and prove that complete denaturation of TMV CP has occurred. Thus, at pH 8.0 TMV CP displays surprisingly low thermostability.…”

“…We have analyzed a new TMV ts mutant, ts21-66, carrying two amino acid substitutions (I21-~T and D66~G) in the CP, and found that it induces formation of small necroses on leaves of N. sylvestris N' [9]. 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).…”

Low sodium dodecyl sulfate concentrations inhibit tobacco mosaic virus coat protein amorphous aggregation and change the protein stability

“…Wild type (strain U1) TMV was obtained as described elsewhere [11] and its coat protein was isolated by the acetic acid method [12]. The CP preparations were stored at concen trations of 4 to 5 mg/ml in 5 mM Na/Na phosphate buffer (PB), pH 8.0, at 4 or -20°C.…”

Misfolded plant virus proteins: elicitors and targets of ubiquitylation

“…Underlined amino acid replacements cause temperature sensitivity of the subunit, non‐underlined ones do not ([8–10,12]; cf. [18]).…”