title: Adenylate cyclase mutations rescue the degP temperature-sensitive phenotype and induce the sigma E and Cpx extracytoplasmic stress regulons in Escherichia coli.
abstract: Inactivation of the gene encoding the periplasmic protease DegP confers a high-temperature-sensitive phenotype in Escherichia coli. We have previously demonstrated that a degP mutant of E. coli strain CBM (W3110 pldA1) is not temperature sensitive and showed that this was most likely due to constitutive activation of the sigma E and Cpx extracytoplasmic stress regulons in the parent strain. In this study, further characterization of this strain revealed a previously unknown cryptic mutation that rescued the degP temperature-sensitive phenotype by inducing the extracytoplasmic stress regulons. We identified the cryptic mutation as an 11-bp deletion of nucleotides 1884 to 1894 of the adenylate cyclase-encoding cyaA gene (cyaAdelta11). The mechanism in which cyaAdelta11 induces the sigma E and Cpx regulons involves decreased activity of the mutant adenylate cyclase. Addition of exogenous cyclic AMP (cAMP) to the growth medium of a cyaAdelta11 mutant strain that contains a Cpx- and sigma E-inducible degP-lacZ reporter fusion decreased beta-galactosidase expression to levels observed in a cyaA+ strain. We also found that a cyaA null mutant displayed even higher levels of extracytoplasmic stress regulon activation compared to a cyaAdelta11 mutant. Thus, we conclude that the lowered concentration of cAMP in cyaA mutants induces both sigma E and Cpx extracytoplasmic stress regulons and thereby rescues the degP temperature-sensitive phenotype.
authors.affiliation: Department of Microbiology and Immunology, 107 Wiggins Road, Room A224, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Timothy G
authors.initials: TG
authors.lastname: Strozen
authors.forename: Geoffrey R
authors.initials: GR
authors.lastname: Langen
authors.forename: S Peter
authors.initials: SP
authors.lastname: Howard
mesh_terms: D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000378:metabolism / Q000502:physiology; D009154:Mutation; D033903:Periplasmic Proteins / Q000502:physiology; D010641:Phenotype; D011494:Protein Kinases / Q000235:genetics; D018085:Regulon; D012697:Serine Endopeptidases / Q000502:physiology; D012808:Sigma Factor / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics*; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; D033903:Periplasmic Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C063202:sporulation-specific sigma factors; C085504:CpxR protein, Bacteria; D011494:Protein Kinases; C092472:CpxA protein, bacteria; C061682:DegP protease; D012697:Serine Endopeptidases; D000262:Adenylyl Cyclases