Regulation of the put operon in Salmonella typhimurium: characterization of promoter and operator mutations

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• The put operon in S. typhimurium is essential for proline utilization.
• Its expression is regulated by proline induction and catabolite repression.
• The putA protein is known to autogenously repress put operon transcription.

Purpose of the Study:

• To elucidate the molecular mechanism governing put operon regulation.
• To identify and characterize regulatory mutations within the put control region.

Main Methods:

• Isolation of regulatory mutants using dehydroproline resistance and put::lacZ operon fusions.
• Assessing the impact of mutations on transcription in both directions via lacZ expression.
• Determining the cis-dominance of mutations and their mapping within the regulatory region.

Main Results:

• Regulatory mutations were identified in the intergenic region between putA and putP.
• Mutations demonstrated cis-dominance, indicating involvement of a regulatory protein.
• Phenotypic analysis suggests a single operator site and overlapping promoters for the putA and putP genes.

Conclusions:

• The put operon is regulated by a single operator site bound by the putA protein.
• Overlapping promoters for putA and putP contribute to the divergent operon's regulation.
• This mechanism provides a comprehensive understanding of proline utilization gene expression in S. typhimurium.