Figure 4.

p4 interacts with bacteria as a monomer or a disulfide-bridged dimer. E. coli HB101 was incubated with lethal (10 μm) or sublethal (3 μm) doses of FITC-p4 for 5 min. A, bacteria were analyzed by fluorescence microscopy following staining with PI (red) to visualize bacterial permeability and Hoechst to visualize DNA (blue). B, interaction of bacteria with the indicated forms of FITC-p4 was analyzed by fluorescence microscopy. C, interaction of bacteria with the indicated forms of FITC-p4 was analyzed by SDS-PAGE, followed by gel imaging. The peptides with or without incubation with bacteria were separated under nonreducing conditions. The fluorescence intensity of FITC-p4 was measured with the ChemiDoc imaging system. The data in each panel are from one experiment and are representative of four independent experiments. D, images of gels from four independent experiments described in C were quantified. Individual data points and the mean ± S.D. are shown as percentage of the indicated forms of FITC-p4 associated with bacteria.