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Allosteric regulation of DegS protease subunits through a shared energy landscape.

ABSTRACT: The PDZ domains of the trimeric DegS protease bind unassembled outer-membrane proteins (OMPs) that accumulate in the Escherichia coli periplasm. This cooperative binding reaction triggers a proteolytic cascade that activates a transcriptional stress response. To dissect the mechanism of allosteric activation, we generated hybrid DegS trimers with different numbers of PDZ domains and/or protease-domain mutations. By studying the chemical reactivity and enzymatic properties of these hybrids, we show that all subunits experience a strongly coupled energetic landscape. For example, OMP peptide binding to a single PDZ domain stimulates active site chemical modification and proteolytic cleavage in the attached and neighboring protease domains. OMP peptide binding relieves inhibitory PDZ interactions, whereas the interfaces between protease domains in the trimeric DegS core mediate positively cooperative activation driven by both substrate binding and inhibition relief.

SUBMITTER: Mauldin RV

PROVIDER: S-EPMC3551985 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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Allosteric regulation of DegS protease subunits through a shared energy landscape.

Mauldin Randall V RV Sauer Robert T RT

Nature chemical biology 20121202 2

The PDZ domains of the trimeric DegS protease bind unassembled outer-membrane proteins (OMPs) that accumulate in the Escherichia coli periplasm. This cooperative binding reaction triggers a proteolytic cascade that activates a transcriptional stress response. To dissect the mechanism of allosteric activation, we generated hybrid DegS trimers with different numbers of PDZ domains and/or protease-domain mutations. By studying the chemical reactivity and enzymatic properties of these hybrids, we sh ...[more]

PMID: 23201899

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Project description:In bacteria, DegS protease functions as an activating factor of the σE envelope stress response system, which ultimately activates the transcription of stress response genes in the cytoplasm. On the basis of high-throughput RNA sequencing, we have previously found that degS knockout inhibits the expression of flagellum synthesis- and chemotaxis-related genes, thereby indicating that DegS may be involved in the regulation of V. cholerae motility. In this study, we examined the relationships between DegS and motility in V. cholerae. Swimming motility and chemotaxis assays revealed that degS or rpoE deletion promotes a substantial reduction in the motility and chemotaxis of V. cholerae, whereas these activities were restored in ΔdegS::degS and ΔdegSΔrseA strains, indicating that DegS is partially dependent on σE to positively regulate V. cholerae activity. Gene-act network analysis revealed that the cAMP-CRP-RpoS signaling pathway, which plays an important role in flagellar synthesis, is significantly inhibited in ΔdegS mutants, whereas in response to the overexpression of cyaA/crp and rpoS in the ΔdegS strain, the motility and chemotaxis of the ΔdegS + cyaA/crp and ΔdegS + rpoS strains were partially restored compared with the ΔdegS strain. We further demonstrated that transcription levels of the flagellar regulatory gene flhF are regulated by DegS via the cAMP-CRP-RpoS signaling pathway. Overexpression of the flhF gene in the ΔdegS strain partially restored motility and chemotaxis. In addition, suckling mouse intestinal colonization experiments indicated that the ΔdegS and ΔrpoE strains were characterized by the poor colonization of mouse intestines, whereas colonization efficacy was restored in the ΔdegSΔrseA, ΔdegS + cyaA/crp, ΔdegS + rpoS, and ΔdegS + flhF strains. Collectively, our findings indicate that DegS regulates the motility and chemotaxis of V. cholerae via the cAMP-CRP-RpoS-FlhF pathway, thereby influencing the colonization of suckling mouse intestines.

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Allosteric regulation of DegS protease subunits through a shared energy landscape.

Publications

Allosteric regulation of DegS protease subunits through a shared energy landscape.

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