Molecular Characterization of the PhoP-PhoQ Two-Component System in Escherichia coli K-12: Identification of Extracellular Mg ²⁺ -Responsive Promoters

Abstract

We identified Mg2+-responsive promoters of thephoPQ, mgtA, and mgrB genes ofEscherichia coli K-12 by S1 nuclease analysis. Expression of these genes was induced by magnesium limitation and depended on PhoP and PhoQ. The transcription start sites were also determined, which allowed us to find a (T/G)GTTTA direct repeat in their corresponding promoter regions.

The connector SafA interacts with the multi‐sensing domain of PhoQ in Escherichia coli

“…The E. coli strains used in this study are listed in Table 1. Strain MG1601 harbours a lacZ gene under control of the PhoP regulated mgtA promoter (Kato et al, 1999). In order to obtain an mgrB-deleted PhoP-reporter strain, we generated MG1655 mgrB by P1 transduction from JW1815 to MG1655 with kanamycin selection.…”

“…1 only indicates whether the two proteins come in close contact. To address whether the two-hybrid interaction between SafA and PhoQ directly correlated with PhoQ activity, we used a reporter strain of the PhoQ/PhoP system, MG1601, carrying lacZ under the control of the mgtA promoter (Kato et al, 1999) ( Fig. 2A).…”

The PhoP/PhoQ system controls the intramacrophage type three secretion system of Salmonella enterica

“…The ssrB promoter region protected by the PhoP protein does not resemble the prototypical PhoP box consensus sequence (T/G)TTTAT-5nt-(T/G)TTTAT characterized in the Escherichia coli mgtA promoter (Kato et al, 1999;Minagawa et al, 2003). However, it is becoming increasingly clear that many PhoP-regulated promoters do not conform to the mgtA promoter model and that atypical PhoP-regulated promoters often require additional proteins to promote gene transcription (Zwir et al, 2005).…”

Environmental signal integration by a modular AND gate

“…The E. coli PhoPQ two-component system responds to the external magnesium concentration. The PhoQ regulator activates the mgrB promoter in the absence of exogenous magnesium (Kato et al, 1999;Minagawa et al, 2003). Quorum sensing systems are used by bacteria to communicate (Bassler and Losick, 2006).…”