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Genetic analysis of the stationary phase‐induced mcb operon promoter in Escherichia coli
Author(s) -
Mao Weimin,
Siegele Deborah A.
Publication year - 1998
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1998.00690.x
Subject(s) - operon , biology , promoter , escherichia coli , transcription (linguistics) , point mutation , genetics , gene , stationary phase , lac operon , stationary point , regulatory sequence , microbiology and biotechnology , transcription factor , mutation , gene expression , mathematical analysis , linguistics , philosophy , chemistry , mathematics , chromatography
A combination of deletion analysis and random mutagenesis was used to identify regulatory elements in P mcb , the stationary phase‐induced promoter of the mcb operon. Our results indicate that P mcb is controlled by at least three different factors, two previously identified and at least one unknown factor, which act at four different sites in the promoter. Sequences between −344 and −164 upstream of the transcriptional start site were required for wild‐type levels of mcb transcription in stationary phase. More dramatic reductions in both exponential and stationary phase expression were observed when sequences from −164 to −54 were deleted. Point mutations located between −105 and −138 decreased both exponential and stationary phase expression. All but one of these mutations decreased OmpR‐dependent activation of P mcb transcription. EmrR, also known as MprA, acts directly or indirectly at sequences downstream of −54 to repress P mcb . A minimal promoter containing sequences from −34 to +79 was still induced ≥10‐fold in stationary phase. Point mutations within this region identified sequences at −8, −11, −30, −31 and −32 as important for P mcb activity. These bases are in the gearbox sequence, present in P mcb and several other stationary phase‐induced Escherichia coli promoters.