BglJ-RcsB heterodimers relieve repression of the Escherichia coli bgl operon by H-NS.
RcsB is the response regulator of the complex Rcs two-component system, which senses perturbations in the outer membrane and peptidoglycan layer. BglJ is a transcriptional regulator whose constitutive expression causes activation of the H-NS- and StpA-repressed bgl (aryl-β,D-glucoside) operon in Escherichia coli. RcsB and BglJ both belong to the LuxR-type family of transcriptional regulators with a characteristic C-terminal DNA-binding domain. Here, we show that BglJ and RcsB interact and form heterodimers that presumably bind upstream of the bgl promoter, as suggested by mutation of a sequence motif related to the consensus sequence for RcsA-RcsB heterodimers. Heterodimerization of BglJ-RcsB and relief of H-NS-mediated repression of bgl by BglJ-RcsB are apparently independent of RcsB phosphorylation. In addition, we show that LeuO, a pleiotropic LysR-type transcriptional regulator, likewise binds to the bgl upstream regulatory region and relieves repression of bgl independently of BglJ-RcsB. Thus, LeuO can affect bgl directly, as shown here, and indirectly by activating the H-NS-repressed yjjQ-bglJ operon, as shown previously. Taken together, heterodimer formation of RcsB and BglJ expands the role of the Rcs two-component system and the network of regulators affecting the bgl promoter.
Institute for Genetics, University of Cologne, Zülpicher Str 47a, 50674 Cologne, Germany.
G Raja
GR
Venkatesh
Frant Carlot
FC
Kembou Koungni
Andreas
A
Paukner
Thomas
T
Stratmann
Birgit
B
Blissenbach
Karin
K
Schnetz
D001483:Base Sequence; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D008969:Molecular Sequence Data; D009876:Operon; D011485:Protein Binding; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
C103411:BglJ protein, E coli; D029968:Escherichia coli Proteins; C529458:FimG protein, E coli; C430340:LeuO protein, E coli; C489568:RcsB protein, E coli; D015534:Trans-Activators; D014157:Transcription Factors; D036781:Fimbriae Proteins