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Journal of Bacteriology, August 2000, p. 4617-4624, Vol. 182, No. 16
Department of Biochemistry, School of
Pharmacy, University of Barcelona, 08028 Barcelona, Spain
Received 13 March 2000/Accepted 2 June 2000
The yiaKLMNOPQRS (yiaK-S) gene cluster of
Escherichia coli is believed to be involved in the
utilization of a hitherto unknown carbohydrate which generates the
intermediate L-xylulose. Transcription of
yiaK-S as a single message from the unique promoter found
upstream of yiaK is proven in this study. The 5' end has
been located at 60 bp upstream from the ATG. Expression of the
yiaK-S operon is controlled in the wild-type strain by a
repressor encoded by yiaJ. No inducer molecule of the
yiaK-S operon has been identified among over 80 carbohydrate or derivative compounds tested, the system being expressed
only in a mutant strain lacking the YiaJ repressor. The
lacZ transcriptional fusions in the genetic background of the mutant strain revealed that yiaK-S is modulated by the
integration host factor and by the cyclic AMP (cAMP)-cAMP receptor
protein (Crp) activator complex. A twofold increase in the induction
was observed during anaerobic growth, which was independent of ArcA or
Fnr. Gel mobility shift assays showed that the YiaJ repressor binds to
a promoter fragment extending from
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Regulation of Expression of the
yiaKLMNOPQRS Operon for Carbohydrate Utilization in
Escherichia coli: Involvement of the Main
Transcriptional Factors
50 to +121. These studies also
showed that the cAMP-Crp complex can bind to two different sites. The
lacZ transcriptional fusions of different fragments of the
promoter demonstrated that binding of cAMP-Crp to the Crp site 1, centered at
106, is essential for yiaK-S expression. The
5' end of the yiaJ gene was determined, and its promoter
region was found to overlap with the divergent yiaK-S
promoter. Expression of yiaJ is autogenously regulated and
reduced by the binding of Crp-cAMP to the Crp site 1 of the
yiaK-S promoter.
*
Corresponding author. Mailing address: Departamento de
Bioquímica, Facultad de Farmacia, Universidad de Barcelona,
Avda. Diagonal 643, 08028 Barcelona, Spain. Phone: 34-93-403 44 96. Fax: 34-93-402 4520. E-mail:
jaguilar{at}farmacia.far.ub.es.
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