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J. Bacteriol., Mar 1995, 1169-1178, Vol 177, No. 5
TL Yahr, AK Hovey, SM Kulich and DW Frank
The transcriptional regulation of the Pseudomonas aeruginosa exoS gene was
investigated. Expression of exoS in P. aeruginosa PA103 was dependent upon
growth in a low-cation environment and the presence of a functional exsA
gene. Promoter fusion analysis indicated that a 285-bp PstI-NsiI fragment,
located 5' of the exoS coding region, contained a functional promoter for
exoS. Expression of the reporter gene was inducible in a low-cation growth
environment and required a functional copy of exsA. Divergent promoters,
coordinately regulated with exoS transcription, were identified within the
PstI-NsiI fragment. A fusion derivative of ExsA, MALA3A2, was shown to bind
directly to the PstI- NsiI probe. DNase I protection analysis demonstrated
that MALA3A2 bound to the intergenic region between the postulated -35
boxes of each promoter region. Northern (RNA) blot analysis with probes
internal to and upstream of exoS demonstrated that separate, coordinately
regulated mRNAs were expressed in P. aeruginosa. These data suggested that
a locus, coregulated with exoS transcription, was located upstream of exoS.
DNA sequence analysis of the exoS upstream region revealed three open
reading frames, ORF 1, ORF 2, and ORF 3. ORF 1 demonstrated significant
homology to the SycE/YerA protein of Yersinia sp. SycE/YerA is postulated
to function as a chaperone for the YopE cytotoxin. The loci encoding YopE
and ExoS show similarities in genetic organization, protein composition,
and regulation.
Copyright © 1995, American Society for Microbiology
Transcriptional analysis of the Pseudomonas aeruginosa exoenzyme S structural gene
Department of Microbiology, Medical College of Wisconsin, Milwaukee.
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