FIG. 1.

VP5* induction permeabilizes bacteria. Bacterial permeabilization following IPTG induction was measured as previously described (12). E. coli BL21(DE3) cells containing pET-6HIS plasmids expressing VP4, VP8*, VP5*, VP5*(248–474), VP5*(265–474), or empty controls were grown to an OD₆₀₀ of 0.2 to 0.4 and induced by the addition of IPTG (1 mM). At the indicated times cells were pelleted, resuspended in LB containing 50 μg of streptomycin per ml and 2 mM ONPG and incubated at 30°C for 10 min (26). Cleaved ONPG in supernatants was assayed spectrophotometrically (OD₄₂₀), and the absorbance was standardized to nanomoles of recombinant expressed protein. This experiment was repeated six times with similar results.