FIG 2.

T3D/T1L L3S2 exhibits increased efficiency of ISVP-to-ISVP* conversion in vitro. (A) T3D and T3D/T1L L3S2 virions (2 × 10¹² particles/ml) were divided into aliquots of equal volume and incubated either at 4°C or over a range of temperatures (65 to 85°C) for 5 min. The reaction mixtures were chilled on ice and digested with 0.10 mg/ml trypsin for 30 min. Following addition of loading dye, the samples were subjected to SDS-PAGE analysis. The positions of major capsid proteins are shown. μ1 runs as μ1C (15). (B) ISVPs (2 × 10¹¹ particles/ml) of T3D or T3D/T1L L3S2 were divided into aliquots of equivalent volume and incubated either at 4°C or over a range of temperatures (22 to 42°C) for 20 min. The reactions were chilled on ice and digested with 0.10 mg/ml trypsin for 30 min. Following addition of loading dye, the samples were subjected to SDS-PAGE analysis. The gels shown are representative of at least 3 independent experiments. The positions of major capsid proteins are shown. μ1 runs as μ1C. (C) ISVPs generated from P2 stocks of the indicated virus strain were divided into aliquots of equivalent volume and incubated at either 4°C or 40°C for 20 min. Reactions were then diluted in PBS and subjected to plaque assay. The data are plotted as mean loss of infectivity for three independent samples in comparison to samples incubated at 4°C. Error bars indicate SD. ***, P < 0.001 in comparison to T3D, as determined by Student's t test.