Fig 2.

Phosphorylated AlgR and AlgR D54E bound to the fimU promoter. The effect of in vitro phosphorylation of AlgR on binding to an 82-bp fimU DNA fragment was compared with the binding of purified AlgR D54N or AlgR D54E using EMSA. (A) Diagram of the 82-bp fragment used in EMSAs and its location within the fimT-fimU intergenic region. (B) Increasing amounts of the phosphate donor, AcP, were added to the AlgR protein in order to determine the effect of phosphorylation on DNA binding. Wild-type AlgR protein was pretreated with AcP for 30 min prior to binding reactions. Lanes 1 to 8, fimU DNA alone (lane 1) or in the presence of AlgR without AcP (lane 2) or with increasing concentrations of AcP (lanes 3 to 8). Lanes 9 to 12, the AlgR-P–DNA complex was competed with the addition of nonradiolabeled fimU DNA. (C) Phosphorylated AlgR protein was compared with untreated AlgR for DNA binding. Purified AlgR protein was pretreated either with water only or with AcP (500× molar excess of protein) prior to binding reactions. Lanes 1 to 10, fimU DNA incubated with a no-protein control (lane 1), increasing concentrations of AlgR (lanes 2 to 5) or AlgR-P (lanes 6 to 9), or 5 mM AcP only (lane 10). Lanes 11 to 13, 5 nM pscEF DNA incubated with a no-protein control (lane 11), 2.5 μM AlgR (lane 12), or 2.5 μM AlgR-P (lane 13). (D) Purified AlgR D54N or AlgR D54E protein was tested for binding to fimU DNA. Lane 1, no-protein control; lanes 2 to 5, increasing concentrations of AlgR D54N; lanes 6 to 9, increasing concentrations of AlgR D54E (lanes 6 to 9). Open arrowheads, unbound DNA; filled arrowheads, AlgR-DNA complexes. All concentrations given in the figure are final binding reaction concentrations.