A new mechanism for the control of a prokaryotic transcriptional regulator: antagonistic binding of positive and negative effectors.
MalT, the transcriptional activator of the Escherichia coli maltose regulon, self-associates, binds promoter DNA and activates initiation of transcription only in the presence of ATP and maltotriose, the inducer. In vivo studies have revealed that MalT action is negatively controlled by the MalY protein. Using a biochemical approach, we analyse here the mechanism whereby MalY represses MalT activity. We show that MalY inhibits transcription activation by MalT in a purified transcription system. In vitro, a constitutive MalT variant (which is partially active in the absence of maltotriose) is less sensitive than wild-type MalT to repression by MalY, as observed in vivo. We demonstrate that MalY forms a complex with MalT only in the absence of maltotriose and that, conversely, MalY inhibits maltotriose binding by MalT. Together, these results establish that MalY acts directly upon MalT without the help of any factor, and that MalY is a negative effector of MalT competing with the inducer for MalT binding.
Schreiber
V
V
Unité de Génétique Moléculaire, URA CNRS 1773, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France.
Steegborn
C
C
Clausen
T
T
Boos
W
W
Richet
E
E
D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology; D001667:Binding, Competitive / Q000187:drug effects; D003542:Cystathionine gamma-Lyase / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D014644:Genetic Variation; D008320:Maltose / Q000378:metabolism; D009154:Mutation; D009711:Nucleotides / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D012097:Repressor Proteins / Q000378:metabolism / Q000502:physiology; D014157:Transcription Factors; D014158:Transcription, Genetic; D014312:Trisaccharides / Q000378:metabolism
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C058976:MalT protein, E coli; D009711:Nucleotides; D012097:Repressor Proteins; D014157:Transcription Factors; D014312:Trisaccharides; C079405:MalY protein, E coli; C008317:maltotriose; D008320:Maltose; D003542:Cystathionine gamma-Lyase