Activation of the Cpx regulon destabilizes the F plasmid transfer activator, TraJ, via the HslVU protease in Escherichia coli.
The Escherichia coli CpxAR two-component signal transduction system senses and responds to extracytoplasmic stress. The cpxA101* allele was previously found to reduce F plasmid conjugation by post-transcriptional inactivation of the positive activator TraJ. Microarray analysis revealed upregulation of the protease-chaperone pair, HslVU, which was shown to degrade TraJ in an E. coli C600 cpxA101* background. Double mutants of cpxA101* and hslV or hslU restored TraJ and F conjugation to wild-type levels. The constitutive overexpression of nlpE, an outer membrane lipoprotein that induces the Cpx stress response, also led to HslVU-mediated degradation of TraJ and repression of F transfer. However, Cpx-mediated TraJ degradation appears to be growth phase-dependent, as induction of nlpE in mid-log phase cells did not appreciably alter TraJ levels. Further, His6-TraJ was sensitive to HslVU degradation in vitro only when it was purified from cells overexpressing nlpE. Thus, TraJ appears to become resistant to HslVU during normal growth, with this resistance mapping to the F transfer region. Extracytoplasmic stress prevents this modification of TraJ, leaving it susceptible to HslVU. Thus, the CpxAR stress response indirectly controls the synthesis of the F mating apparatus, a complex transenvelope type IV secretion system, by degrading TraJ.
Lau-Wong
Isabella C
IC
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9.
Locke
Troy
T
Ellison
Michael J
MJ
Raivio
Tracy L
TL
Frost
Laura S
LS
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003227:Conjugation, Genetic; D049071:Endopeptidase Clp / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005144:F Factor; D017353:Gene Deletion; D020869:Gene Expression Profiling; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D018085:Regulon
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C483566:ClpYQ protease, E coli; D029968:Escherichia coli Proteins; D008074:Lipoproteins; C095021:NlpE protein, E coli; C488999:TraJ protein, E coli; C085504:CpxR protein, Bacteria; D011494:Protein Kinases; C490475:CpxA protein, E coli; D049071:Endopeptidase Clp