Journal article
Functional Domains of ExsA, the Transcriptional Activator of the Pseudomonas aeruginosa Type III Secretion System
Journal of bacteriology, Vol.191(12), pp.3811-3821
06/2009
DOI: 10.1128/JB.00002-09
PMCID: PMC2698394
PMID: 19376850
Abstract
The opportunistic pathogen
Pseudomonas aeruginosa
utilizes a type III secretion system (T3SS) to evade phagocytosis and damage eukaryotic cells. Transcription of the T3SS regulon is controlled by ExsA, a member of the AraC/XylS family of transcriptional regulators. These family members generally consist of an ∼100-amino acid carboxy-terminal domain (CTD) with two helix-turn-helix DNA binding motifs and an ∼200-amino acid amino-terminal domain (NTD) with known functions including oligomerization and ligand binding. In the present study, we show that the CTD of ExsA binds to ExsA-dependent promoters in vitro and activates transcription from ExsA-dependent promoters both in vitro and in vivo. Despite possessing these activities, the CTD lacks the cooperative binding properties observed for full-length ExsA at the P
exsC
promoter. In addition, the CTD is unaffected by the negative regulatory activity of ExsD, an inhibitor of ExsA activity. Binding studies confirm that ExsD interacts directly with the NTD of ExsA. Our data are consistent with a model in which a single ExsA molecule first binds to a high-affinity site on the P
exsC
promoter. Protein-protein interactions mediated by the NTD then recruit an additional ExsA molecule to a second site on the promoter to form a complex capable of stimulating wild-type levels of transcription. These findings provide important insight into the mechanisms of transcriptional activation by ExsA and inhibition of ExsA activity by ExsD.
Details
- Title: Subtitle
- Functional Domains of ExsA, the Transcriptional Activator of the Pseudomonas aeruginosa Type III Secretion System
- Creators
- Evan D Brutinel - Department of Microbiology, University of Iowa, Iowa City, IowaChristopher A Vakulskas - Department of Microbiology, University of Iowa, Iowa City, IowaTimothy L Yahr - Department of Microbiology, University of Iowa, Iowa City, Iowa
- Resource Type
- Journal article
- Publication Details
- Journal of bacteriology, Vol.191(12), pp.3811-3821
- DOI
- 10.1128/JB.00002-09
- PMID
- 19376850
- PMCID
- PMC2698394
- NLM abbreviation
- J Bacteriol
- ISSN
- 0021-9193
- eISSN
- 1098-5530
- Publisher
- American Society for Microbiology (ASM)
- Language
- English
- Date published
- 06/2009
- Academic Unit
- Microbiology and Immunology
- Record Identifier
- 9984001143302771
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