Biochemical characterization of a regulatory cascade controlling transcription of the Pseudomonas aeruginosa type III secretion system

Zhida Zheng; Guozhou Chen; Shreyas Joshi; Evan D Brutinel; Timothy L Yahr; Lingling Chen

doi:10.1074/jbc.M611664200

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Biochemical characterization of a regulatory cascade controlling transcription of the Pseudomonas aeruginosa type III secretion system

Journal article

Open access

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Biochemical characterization of a regulatory cascade controlling transcription of the Pseudomonas aeruginosa type III secretion system

Zhida Zheng, Guozhou Chen, Shreyas Joshi, Evan D Brutinel, Timothy L Yahr and Lingling Chen

The Journal of biological chemistry, Vol.282(9), pp.6136-6142

03/02/2007

DOI: 10.1074/jbc.M611664200

PMID: 17197437

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Abstract

Many Gram-negative pathogens utilize type III secretion systems (T3SS) to translocate effector proteins into eukaryotic host cells. Expression of T3SS genes is highly regulated and is often coupled to type III secretory activity. Transcription of the Pseudomonas aeruginosa T3SS genes is coupled to secretion by a cascade of interacting regulatory proteins (ExsA, ExsD, ExsC, and ExsE). ExsA is an activator of type III gene transcription, ExsD binds ExsA to inhibit transcription, ExsC inhibits ExsD activity, and ExsE inhibits ExsC activity. The entire process is coupled to secretion by virtue of the fact that ExsE is a secreted substrate of the T3SS. Changes in the intracellular concentration of ExsE are thought to govern formation of the ExsC-ExsE, ExsC-ExsD, and ExsD-ExsA complexes. Whereas formation of the ExsC-ExsE complex allows ExsD to bind ExsA and transcription of the T3SS is repressed, formation of the ExsC-ExsD complex sequesters ExsD from ExsA and transcription of the T3SS is induced. In this study, we characterized the self-association states of ExsC, ExsD, and ExsE and the binding interactions of ExsC with ExsE and ExsD. ExsC exists as a homodimer and binds one molecule of ExsE substrate. Dimeric ExsC also interacts directly with ExsD to form a heterotetrameric complex. The difference in binding affinities between the ExsC-ExsE (K(d) 1 nm) and ExsC-ExsD (K(d) 18 nm) complexes supports a model in which ExsC preferentially binds cytoplasmic ExsE, resulting in the inhibition of T3SS gene transcription.

Bodily Secretions

Transcription Factors - metabolism

Transcription Factors - physiology

Pseudomonas aeruginosa - genetics

Repressor Proteins

Trans-Activators

Protein Binding

Transcription, Genetic

Recombinant Fusion Proteins

Bacterial Proteins

Multiprotein Complexes - physiology

Details

Title: Subtitle: Biochemical characterization of a regulatory cascade controlling transcription of the Pseudomonas aeruginosa type III secretion system
Creators: Zhida Zheng - Department of Biology, Iniana University, Bloomington, Indiana 47405, USA
Guozhou Chen
Shreyas Joshi
Evan D Brutinel
Timothy L Yahr
Lingling Chen
Resource Type: Journal article
Publication Details: The Journal of biological chemistry, Vol.282(9), pp.6136-6142
DOI: 10.1074/jbc.M611664200
PMID: 17197437
NLM abbreviation: J Biol Chem
ISSN: 0021-9258
eISSN: 1083-351X
Publisher: United States
Grant note: R01-AI055042 / NIAID NIH HHS R01-GM065260-01A1 / NIGMS NIH HHS R01 AI055042 / NIAID NIH HHS
Language: English
Date published: 03/02/2007
Academic Unit: Microbiology and Immunology
Record Identifier: 9984001200402771

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