TY - JOUR

T1 - Tandem DNA-bound cAMP-CRP complexes are required for transcriptional repression of the deoP2 promoter by the CytR repressor in Escherichia coli

AU - Søgaard-Andersen, Lotte

AU - Møllegaard, N E

AU - Douthwaite, S R

AU - Valentin-Hansen, P

N1 - Keywords: Bacterial Proteins; Base Sequence; Binding Sites; Cyclic AMP; Cyclic AMP Receptor Protein; DNA, Bacterial; Escherichia coli; Escherichia coli Proteins; Genes, Bacterial; Molecular Sequence Data; Mutation; Promoter Regions, Genetic; Repressor Proteins; Transcription, Genetic

PY - 1990

Y1 - 1990

N2 - We have studied the deoP2 promoter in Escherichia coli to define features important for its interaction with the CytR repressor. As is characteristic for CytR-regulated promoters, deoP2 encodes tandem binding sites for the activating complex cAMP-CRP. One of these sites, CRP-1, overlaps the -35 region, and is sufficient for activation; the second site, CRP-2, centred around -93, is indispensable for repression. Here we demonstrate, by means of in vivo titration, that CytR interaction with deoP2 depends not only on CRP-2, but also on CRP-1 and the length and possibly the sequence separating these two sites. Also, point mutations in either CRP site reduce or abolish CytR titration; however, no co-operativity is observed in the interaction of CytR with the two CRP binding sites. Furthermore, the reduction in CytR titration parallels the reduction in binding of cAMP-CRP to the mutated CRP sites in vitro. These observations are not easily explained by current models for the action of prokaryotic repressors; instead we favour a model in which the interaction of CytR with deoP2 depends on the presence of tandem DNA-bound cAMP-CRP complexes.

AB - We have studied the deoP2 promoter in Escherichia coli to define features important for its interaction with the CytR repressor. As is characteristic for CytR-regulated promoters, deoP2 encodes tandem binding sites for the activating complex cAMP-CRP. One of these sites, CRP-1, overlaps the -35 region, and is sufficient for activation; the second site, CRP-2, centred around -93, is indispensable for repression. Here we demonstrate, by means of in vivo titration, that CytR interaction with deoP2 depends not only on CRP-2, but also on CRP-1 and the length and possibly the sequence separating these two sites. Also, point mutations in either CRP site reduce or abolish CytR titration; however, no co-operativity is observed in the interaction of CytR with the two CRP binding sites. Furthermore, the reduction in CytR titration parallels the reduction in binding of cAMP-CRP to the mutated CRP sites in vitro. These observations are not easily explained by current models for the action of prokaryotic repressors; instead we favour a model in which the interaction of CytR with deoP2 depends on the presence of tandem DNA-bound cAMP-CRP complexes.

M3 - Journal article

C2 - 1962841

VL - 4

SP - 1595

EP - 1601

JO - Molecular Microbiology

JF - Molecular Microbiology

SN - 0950-382X

IS - 9

ER -