Dataset Information

Characterization of degQ and degS, Escherichia coli genes encoding homologs of the DegP protease.

ABSTRACT: The degQ and degS genes of Escherichia coli encode proteins of 455 and 355 residues, respectively, which are homologs of the DegP protease. The purified DegQ protein has the properties of a serine endoprotease and is processed by the removal of a 27-residue amino-terminal signal sequence. A plasmid expressing degQ rescues the temperature-sensitive phenotype of a strain bearing the degP41 deletion, implying that DegQ, like DegP, functions as a periplasmic protease in vivo. Deletions in the degQ gene cause no obvious growth defect, while those in the degS gene result in a small-colony phenotype. The latter phenotype is rescued by a plasmid expressing the degS gene but not by plasmids expressing the degQ or degP genes. This result and the inability of a plasmid expressing degS to rescue the temperature-sensitive degP41 phenotype indicate that the DegS protein is functionally different from the DegQ and DegP proteins.

SUBMITTER: Waller PR

PROVIDER: S-EPMC177778 | biostudies-other | 1996 Feb

REPOSITORIES: biostudies-other

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Characterization of degQ and degS, Escherichia coli genes encoding homologs of the DegP protease.

Waller P R PR Sauer R T RT

Journal of bacteriology 19960201 4

The degQ and degS genes of Escherichia coli encode proteins of 455 and 355 residues, respectively, which are homologs of the DegP protease. The purified DegQ protein has the properties of a serine endoprotease and is processed by the removal of a 27-residue amino-terminal signal sequence. A plasmid expressing degQ rescues the temperature-sensitive phenotype of a strain bearing the degP41 deletion, implying that DegQ, like DegP, functions as a periplasmic protease in vivo. Deletions in the degQ g ...[more]

PMID: 8576051

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Project description:In Escherichia coli, the periplasmic protease DegP plays a critical role in degrading misfolded outer membrane proteins (OMPs). Consequently, mutants lacking DegP display a temperature-sensitive growth defect, presumably due to the toxic accumulation of misfolded OMPs. The Tol-Pal complex plays a poorly defined but an important role in envelope biogenesis, since mutants defective in this complex display a classical periplasmic leakage phenotype. Double mutants lacking DegP and an intact Tol-Pal complex display exaggerated temperature-sensitive growth defects and the leaky phenotype. Two revertants that overcome the temperature-sensitive growth phenotype carry missense mutations in the degS gene, resulting in D102V and D320A substitutions. D320 and E317 of the PDZ domain of DegS make salt bridges with R178 of DegS's protease domain to keep the protease in the inactive state. However, weakening of the tripartite interactions by D320A increases DegS's basal protease activity. Although the D102V substitution is as effective as D320A in suppressing the temperature-sensitive growth phenotype, the molecular mechanism behind its effect on DegS's protease activity is unclear. Our data suggest that the two DegS variants modestly activate RseA-controlled, σE-mediated envelope stress response pathway and elevate periplasmic protease activity to restore envelope homeostasis. Based on the release of a cytoplasmic enzyme in the culture supernatant, we conclude that the conditional lethal phenotype of ΔtolB ΔdegP mutants stems from a grossly destabilized envelope structure that causes excessive cell lysis. Together, the data point to a critical role for periplasmic proteases when the Tol-Pal complex-mediated envelope structure and/or functions are compromised.IMPORTANCE The Tol-Pal complex plays a poorly defined role in envelope biogenesis. The data presented here show that DegP's periplasmic protease activity becomes crucial in mutants lacking the intact Tol-Pal complex, but this requirement can be circumvented by suppressor mutations that activate the basal protease activity of a regulatory protease, DegS. These observations point to a critical role for periplasmic proteases when Tol-Pal-mediated envelope structure and/or functions are perturbed.

Dataset Information

Characterization of degQ and degS, Escherichia coli genes encoding homologs of the DegP protease.

Publications

Characterization of degQ and degS, Escherichia coli genes encoding homologs of the DegP protease.

Similar Datasets

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