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The structure of an ECF‐σ‐dependent, light‐inducible promoter from the bacterium Myxococcus xanthus
Author(s) -
MartínezArgudo Isabel,
RuizVázquez Rosa M.,
Murillo Francisco J.
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.1365-2958.1998.01129.x
Subject(s) - myxococcus xanthus , promoter , biology , dna , subfamily , enhancer , gene , genetics , transcription factor , gene expression , mutant
Expression of the Myxococcus xanthus gene crtI is controlled by a light‐inducible promoter. The activity of this promoter depends on CarQ, a σ factor of the extracytoplasmic function (ECF) subfamily. Here, we show that the minimum DNA stretch reproducing normal expression of crtI extends from a few bases upstream of the −35 position to a site well downstream of the transcriptional start. The downstream DNA contains an enhancer‐like element that remains active when displaced upstream of the promoter. Experimental evidence is provided for the activity of the crtI promoter being critically dependent on a pentanucleotide sequence centred at the −31 position. The similarity of this sequence with the consensus for ECF‐σ‐dependent promoters from other bacteria is discussed. The activity of the crtI promoter also depends on certain basepairs at the −10 region. Hence, the operation of ECF‐σ‐factors seems to require binding to two different DNA sites, although the −10 sequences of different ECF‐σ‐dependent promoters are unrelated to one another, and the ECF‐σ‐factors themselves lack the conserved domain known to mediate binding of other σ‐factors to the −10 DNA site.