cAMP-CRP activator complex and the CytR repressor protein bind co-operatively to the cytRP promoter in Escherichia coli and CytR antagonizes the cAMP-CRP-induced DNA bend.
Initiation of transcription from the cytRP promoter in Escherichia coli is activated by the cAMP-CRP complex and negatively regulated by the CytR repressor protein. By combining gel retardation and footprinting assays, we show that cAMP-CRP binds to a single site centered at position -64 and induces a considerable bend in the DNA. CytR binds to a region immediately downstream from, and partially overlapping, the CRP site, and induces a modest bend into the DNA. In combination, cAMP-CRP and CytR bind co-operatively to cytRP forming a nucleoprotein complex in which the proteins directly interact with each other and bind to the same face of the DNA helix. CytR binding concomitantly antagonizes the cAMP-CRP-induced bend. This study indicates that the minimal DNA region required to obtain CytR regulation consists of a single binding site for each of cAMP-CRP and CytR. The case described here, in which a protein-induced DNA bend is modulated by a second protein, may illustrate a mechanism that applies to other regulatory systems.
Pedersen
H
H
Department of Molecular Biology, Odense University, Denmark.
Søgaard-Andersen
L
L
Holst
B
B
Gerlach
P
P
Bremer
E
E
Valentin-Hansen
P
P
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000242:Cyclic AMP / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002373:Cyclic AMP Receptor Protein; D003562:Cytidine / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011953:Receptors, Cyclic AMP / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein; C048425:CytR protein, E coli; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D011953:Receptors, Cyclic AMP; D012097:Repressor Proteins; D003562:Cytidine; D000242:Cyclic AMP