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Multiple transcribed elements control expression of the Escherichia coli btuB gene
1Department of Microbiology, University of Virginia School of Medicine, Charlottesville 22908, USA.
Journal of Bacteriology
|June 1, 1997
Summary
Vitamin B12 represses the BtuB cobalamin transporter in E. coli via transcriptional and translational control. Specific leader sequences and an attenuator are crucial for this regulation, with long-range interactions influencing expression.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Escherichia coli utilizes the BtuB protein in its outer membrane for cobalamin (vitamin B12) transport.
- Vitamin B12 acts as a repressor for BtuB expression, indicating a regulatory mechanism to control nutrient uptake.
Purpose of the Study:
- To investigate the molecular mechanisms underlying vitamin B12-mediated repression of the cobalamin transporter BtuB in E. coli.
- To identify the specific DNA sequences within the btuB leader and coding regions responsible for transcriptional and translational control.
Main Methods:
- Utilized lac fusions to study the effects of deletions within the btuB regulatory region on gene expression and repression.
- Analyzed the role of 5' transcript elements and a putative attenuator in transcriptional repression.
Main Results:
- Transcriptional repression of btuB by vitamin B12 involves elements at the 5' end of the transcript and a putative attenuator.
- Deletions in these regions significantly altered btuB-lacZ expression.
- A conserved leader sequence element could reverse the repression, highlighting the importance of long-range interactions.
Conclusions:
- Vitamin B12 repression of BtuB is a complex process involving both transcriptional and translational control.
- Specific sequences in the btuB leader and coding regions, including long-range interactions, are critical for this regulation.