title: Analysis of the effect exerted by extracellular pH on the maltose regulon in Escherichia coli K-12.
abstract: The Escherichia coli maltose regulon consists of five operons under the control of the MalT transcriptional activator. lac operon fusions were constructed in vitro with the MalT-dependent promoter and with the malT promoter itself. beta-Galactosidase activity displayed by these fusions during growth at different external pH (pHo) revealed that growth at a pHo higher than 6 stimulates the transcription of malT- and MalT-controlled genes in the absence or presence of maltose. Using a malTp1 malTp10 promoter that is cAMP-CRP (cAMP receptor protein)-independent, it was demonstrated that CRP is essential for malT pHo regulation and that the pHo-dependent activity of malKp is a direct consequence of malT regulation. The pHo regulation displayed by a deleted but still functional malT promoter fused to lacZ demonstrates that this minimal promoter contains all the regulatory regions for establishing pHo regulation. In the absence of MIc, a repressor of malT expression, the pHo regulation of malT was still effective. It is proposed that binding of cAMP-CRP at malTp may be affected by malTp topology induced by pHo or that a pHo-dependent effector may act in concert with the cAMP-CRP complex.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Alonzo
authors.forename: Martine
authors.initials: M
authors.lastname: Heyde
authors.forename: Patrick
authors.initials: P
authors.lastname: Laloi
authors.forename: Raymond
authors.initials: R
authors.lastname: Portalier
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein / Q000502:physiology; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D008320:Maltose / Q000502:physiology*; D018085:Regulon; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C068021:MalK protein, Bacteria; C489398:MalK protein, E coli; C058976:MalT protein, E coli; D014157:Transcription Factors; D008320:Maltose