Fractionation of membrane preparations was achieved using sucrose density gradients

as previously described [39]. Immunoprecipitation Immunoprecipitations with EPEC cell lysates were performed as previously described [39]. Briefly, 500 ng of affinity purified polyclonal anti-CesT antibody was added to 50 μl of Protein A conjugated agarose beads (Invitrogen) followed by washing as directed by the manufacturer. The antibody-bead mixture was blocked in phosphate buffered saline (PBS, 137 mM NaCl, 2.7 mM KCl, 4.3 mM Na2HPO4, 1.47 mM KH2PO4) supplemented with 1% (w/v) bovine serum albumin and then added to lysate preparations and incubated overnight at 4°C on a rotator. The samples MK0683 mouse were gently pelleted and the agarose beads were washed 3 times with PBS. The agarose beads were then exposed to 100 mM glycine (pH 2.2) to elute bound proteins and neutralized with 1 M Tris (pH 8.8) and then prepared for SDS-PAGE. Infection of HeLa cells HeLa cells [American Type Culture Collection (ATCC)] were seeded onto sterile glass coverslips at a density of 1 × 105 /ml, grown for 24 hrs and then infected with various EPEC strains at a multiplicity of infection of 50 for 3 hours. The infected HeLa cells were then prepared for microscopy as previously described [35]. Images were GSI-IX chemical structure detected using a Zeiss Axiovert 200 inverted

microscope and captured using a Hamamatsu ORCA-R2 digital camera. Microscopy based quantification of EPEC intimate adherence (binding index) was performed as previously selleckchem described [67]. Briefly, GFP positive bacteria (which were identified by GFP fluorescence) that were associated with actin pedestals were quantified. At least 50 cells were examined per sample. β-lactamase reporter assays Type III effector-TEM1 fusion reporter assays for EPEC strains were performed as previously described [42] with minor modifications. Briefly, HeLa cells (seeded to confluence in 96 well, black, clear bottom plates [Costar 3603]) were infected with a MOI of approximately 50 for 2 hours using bacteria that

had been pre-activated in DMEM +10% FBS for 2 hours at 37°C, 5% CO2. After 1 hour of infection, IPTG was added to a final concentration of 0.5 mM. The infected cells were gently washed twice with DMEM and then loaded with CCF2/AM using a Toxblazer kit (Invitrogen). The 96 3-oxoacyl-(acyl-carrier-protein) reductase well plate was incubated for 90 min in the dark and then placed in a Victor X plate reader (Perkin Elmer) set to read fluorescence using an excitation filter for 405 nm and emission filters for 460 nm (blue signal)/530 nm (green signal). Blue/green signal ratios and statistical significance (two sided Student’s t test) were calculated as previously described [42]. The presented data are mean values of the results from three experiments. Protein electrophoresis and Immunoblotting All protein samples were separated by SDS-PAGE as described [68].