FIG. 1.

Expression of M1 mutant proteins and ts phenotype of mutant viruses. (A) cDNA-transfected 293T cells were pulse-labeled at 18 h posttransfection for 2 h. Cells were then lysed in radioimmunoprecipitation assay buffer, immunoprecipitated with anti-M1 antibody, and resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. (B) MDCK cells were infected with A(144-147), F144A, G145A, or T150A virus at an MOI of 0.001 and maintained in VGM containing 0.5 μg/ml trypsin at either 33°C or 39.5°C. Supernatants were collected at 48 h p.i. and assayed for virus titer by plaque assay. Data represent mean titers (n = 3). *, P < 0.001 (versus 33°C).