The structure of an ECF-sigma-dependent, light-inducible promoter from the bacterium Myxococcus xanthus.
Expression of the Myxococcus xanthus gene crtl is controlled by a light-inducible promoter. The activity of this promoter depends on CarQ, a sigma factor of the extracytoplasmic function (ECF) subfamily. Here, we show thatthe minimum DNA stretch reproducing normal expression of crtl 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 crtl promoter being critically dependent on a pentanucleotide sequence centred at the -31 position. The similarity of this sequence with the consensus for ECF-sigma-dependent promoters from other bacteria is discussed. The activity of the crtl promoter also depends on certain basepairs at the -10 region. Hence, the operation of ECF-sigma-factors seems to require binding to two different DNA sites, although the -10 sequences of different ECF-sigma-dependent promoters are unrelated to one another, and the ECF-sigma-factors themselves lack the conserved domain known to mediate binding of other sigma-factors to the -10 DNA site.
Martínez-Argudo
I
I
Departamento de Genética y Microbiología, Facultad de Biologia, Universidad de Murcia, Spain.
Ruiz-Vázquez
R M
RM
Murillo
F J
FJ
D001665:Binding Sites; D008027:Light; D016297:Mutagenesis, Site-Directed; D016941:Myxococcus xanthus / Q000235:genetics*; D010641:Phenotype; D010957:Plasmids; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000378:metabolism*; D014158:Transcription, Genetic
D012808:Sigma Factor