title: Cpx signal transduction is influenced by a conserved N-terminal domain in the novel inhibitor CpxP and the periplasmic protease DegP.
abstract: In Escherichia coli, envelope stress can be overcome by three different envelope stress responses: the sigma(E) stress response and the Bae and Cpx two-component systems. The Cpx envelope stress response is controlled by the sensor kinase CpxA, the response regulator CpxR, and the novel periplasmic protein CpxP. CpxP mediates feedback inhibition of the Cpx pathway through a hypothetical interaction with the sensing domain of CpxA. No informative homologues of CpxP are known, and thus it is unclear how CpxP exerts this inhibition. Here, we identified six cpxP loss-of-function mutations using a CpxP-beta-lactamase (CpxP'-'Bla) translational fusion construct. These loss-of-function mutations identified a highly conserved, predicted alpha-helix in the N-terminal domain of CpxP that affects both the function and the stability of the protein. In the course of this study, we also found that CpxP'-'Bla stability is differentially controlled by the periplasmic protease DegP in response to inducing cues and that mutation of degP diminishes Cpx pathway activity. We propose that the N-terminal alpha-helix is an important functional domain for inhibition of the Cpx pathway and that CpxP is subject to DegP-dependent proteolysis.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada.
authors.forename: Daelynn R
authors.initials: DR
authors.lastname: Buelow
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Raivio
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D033903:Periplasmic Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012697:Serine Endopeptidases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D001618:beta-Lactamases / Q000235:genetics
chemical_list: C491730:CpxP protein, E coli; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D033903:Periplasmic Proteins; C061682:DegP protease; D012697:Serine Endopeptidases; D001618:beta-Lactamases