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J. Bacteriol., 12 1997, 7705-7711, Vol 179, No. 24
I Sa-Nogueira and SS Ramos
The Bacillus subtilis araR locus (mapped at about 294 degrees on the
genetic map) comprises two open reading frames with divergently arranged
promoters, the regulatory gene, araR, encoding a repressor, and a partially
cloned gene, termed araE by analogy to the Escherichia coli L-arabinose
permease gene. Here, we report the cloning and sequencing of the entire
araE gene encoding a 50.4-kDa polypeptide. The araE gene is monocistronic
(as determined by Northern blot analysis), and its putative product is very
similar to a number of prokaryotic proton-linked monosaccharide
transporters (the group I family of membrane transport proteins).
Insertional inactivation of the araE gene leads to a conditional Ara-
phenotype dependent on the concentration of L-arabinose in the medium.
Therefore, we assume that araE encodes a permease involved in L-arabinose
transport into the cell. The araE promoter region contains -10 and -35
regions (as determined by primer extension analysis) very similar to those
recognized by RNA polymerase containing the major vegetative-cell sigma
factor sigmaA, and the -35 region of the transcription start point for araE
is located 2 bp from the -35 region of the araR gene. Transcriptional
studies demonstrated that the expression from the araE promoter is induced
by L-arabinose, repressed by glucose, and negatively regulated by AraR.
These observations are consistent with a model according to which in the
absence of L-arabinose, AraR binds to a site(s) within the araE/araR
promoter, preventing transcription from the araE promoter and
simultaneously limiting the frequency of initiation from its own promoter;
the addition of L-arabinose will allow transcription from the araE promoter
and increase the frequency of initiation from the araR promoter.
Copyright © 1997, American Society for Microbiology
Cloning, functional analysis, and transcriptional regulation of the Bacillus subtilis araE gene involved in L-arabinose utilization
Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Oeiras, Portugal. sanoguei@itqb.unl.pt
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