Affiliation:
1. Département de Microbiologie Fondamentale, Université de Lausanne, CH-1015 Lausanne, Switzerland
2. Department of Biology, Georgia State University, Atlanta, Georgia 30303
Abstract
ABSTRACT
In
Pseudomonas aeruginosa
, the CbrA/CbrB two-component system is instrumental in the maintenance of the carbon-nitrogen balance and for growth on carbon sources that are energetically less favorable than the preferred dicarboxylate substrates. The CbrA/CbrB system drives the expression of the small RNA CrcZ, which antagonizes the repressing effects of the catabolite repression control protein Crc, an RNA-binding protein. Dicarboxylates appear to cause carbon catabolite repression by inhibiting the activity of the CbrA/CbrB system, resulting in reduced
crcZ
expression. Here we have identified a conserved palindromic nucleotide sequence that is present in upstream activating sequences (UASs) of promoters under positive control by CbrB and σ
54
RNA polymerase, especially in the UAS of the
crcZ
promoter. Evidence for recognition of this palindromic sequence by CbrB was obtained
in vivo
from mutational analysis of the
crcZ
promoter and
in vitro
from electrophoretic mobility shift assays using
crcZ
promoter fragments and purified CbrB protein truncated at the N terminus. Integration host factor (IHF) was required for
crcZ
expression. CbrB also activated the
lipA
(lipase) promoter, albeit less effectively, apparently by interacting with a similar but less conserved palindromic sequence in the UAS of
lipA
. As expected, succinate caused CbrB-dependent catabolite repression of the
lipA
promoter. Based on these results and previously published data, a consensus CbrB recognition sequence is proposed. This sequence has similarity to the consensus NtrC recognition sequence, which is relevant for nitrogen control.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
42 articles.
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