Anti-activator ExsD forms a 1:1 complex with ExsA to inhibit transcription of type III secretion operons.

ABSTRACT: The ExsA protein is a Pseudomonas aeruginosa transcriptional regulator of the AraC/XylS family that is responsible for activating the type III secretion system operons upon host cell contact. Its activity is known to be controlled in vivo through interaction with its negative regulator ExsD. Using a heterologous expression system, we demonstrated that ExsD is sufficient to inhibit the transcriptional activity of ExsA. Gel shift assays with ExsA- and ExsD-containing cytosolic extracts revealed that ExsD does not block DNA target sites but affects the DNA binding activity of the transcriptional activator. The ExsA-ExsD complex was purified after coproduction of the two partners in Escherichia coli. Size exclusion chromatography and ultracentrifugation analysis revealed a homogeneous complex

SUBMITTER: Thibault J 

PROVIDER: S-EPMC2708873 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature