0, IPTG was added to a final concentration of 1 mM. After a 2-hr induction, bacteria were harvested by centrifugation at 6,500 × g for 20 min and then resuspended in HB

buffer (20 mM Tris, 150 mM NaCl, 30 mM imidazole, pH8.0). The resuspended bacteria were lysed with a French Pressure Cell (SLM Instruments, Inc. Urbane, IL), and the cell lysate was centrifuged at 48,000 × g for 1 hour. The clarified supernatant was passed through a ProBond™ nickel-nitrilotriacetic acid resin affinity column (Invitrogen, Carlsbad, CA) to purify the His6-tagged ColE7/ImE7 according to manufacture’s Palbociclib price protocol (Invitrogen, Carlsbad, CA). Antibody preparation for detection of protein whose expression is affected by gadXY To prepare antibodies against envelope proteins BtuB, TolQ, TolR, TolA, TolB, Pal, and OmpF, the coding region of each protein was fused inframe with His6-tag in the plasmid pQE30 (Qiagen), respectively. The His6-tagged proteins were then expressed and purified using the same method as described for His6-tagged ColE7/ImE7

and sent to the company to prepare polyclonal antibodies. The specificities of these antibodies were confirmed by Western blotting using these antibodies as reported by Pan et. al[49]. DNA binding assay The electrophoretic mobility shift assay was performed to investigate binding of GadX to the btuB promoter. To obtain purified MalE-GadX protein, E. coli strain XL-1 Blue containing pMalE-GadX was grown in 100 ml of LB containing ampicillin (50 μg/ml) and 0.2% glucose to OD600 ~1.0. IPTG was then added to a final concentration of 1 mM. After 2 hr of incubation, the cells were pelleted, resuspended Kinase Inhibitor Library in maltose binding buffer (20 mM

Tris-HCl pH 8.0, 200 Sodium butyrate mM NaCl), and lysed with a French Pressure Cell. The cell lysate was centrifuged at 48,000 × g for 1 hr, and the supernatant was subjected to an amylose resin affinity chromatography (New England BioLabs) to purify the MalE-GadX protein. To make probes for the DNA binding assay, a 461-bp (Figure 3, -219 – +242) DNA fragment containing the btuB promoter was amplified with primers F/btuB-219-XbaI and R/btuB+242-HindIII (Table 5) by PCR. The DNA fragment containing the promoter of gadA (-176 – +77, 253 bp) or gadB (-173 – +77, 250 bp) was used as the positive control, which were amplified with primer pairs F/gadA-176 and R/gadA+77 and F/gadB-173 and R/gadB+77 (Table 5), respectively, as described by Tramonti et al. [19]. The DNA fragment containing the upstream noncoding region of pal was used as the negative control, which was amplified with primers F/pal-XbaI and R/pal-HindIII (Table 5). These DNA fragments were end-labeled with [γ-32P] ATP by T4 polynucleotide kinase (New England BioLabs). The labeled DNA fragments (6 fmol) were incubated with the MalE-GadX protein at room temperature for 20 min in 10 μl of binding buffer [19]. Samples were then loaded on a 5% nondenaturing polyacrylamide gel in 0.5X TBE buffer and electrophoresed for 35 min at room temperature.