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. 2004 Dec;78(24):14057–14061. doi: 10.1128/JVI.78.24.14057-14061.2004

FIG. 3.

FIG. 3.

Selective growth of λ in E. coli cells coexpressing the β-Gal-SCoV 3C-like protease construct and the cI.SCoV repressor. Expression of the protease was induced with IPTG for 1 h, and the cells were infected with λ for three additional hours. The graph illustrates the resulting phage titer per microliter. Plasmids pBSK− and pAlterEX-2 were used as controls for the β-Gal-SCoV 3C-like protease construct and the cI.SCoV repressor, respectively. cI.SCoVmt was also used as a negative control for the cI.SCoV repressor. As shown, selection in cells coexpressing the β-Gal-SCoV 3C-like protease construct and the cI.SCoV3 repressor resulted in λ replication, whereas the replication of λ was severely compromised in cells expressing the mutant cI.SCoVmt repressor. Lack of phage replication was also observed in cells expressing mutated forms of β-Gal-SCoV 3C-like protease that included catalytic-site residue substitutions C145A and H41A. Similarly, expression of another protease (HCV serine protease) also prevented phage replication. Values are the means ± standard deviations (error bars) of at least four experiments.