Effect of fur on pyrC gene expression

Area of Science:

• Molecular Biology
• Microbial Genetics
• Gene Regulation

Background:

• The pyrC gene encodes dihydroorotase, a key enzyme in pyrimidine biosynthesis.
• Understanding gene regulation in Escherichia coli is crucial for metabolic studies.
• The Fur (ferric uptake regulator) protein typically controls iron-related genes.

Purpose of the Study:

• To investigate the role of the Fur protein in the regulation of the Escherichia coli pyrC gene.
• To determine the in vivo expression patterns of pyrC under different genetic backgrounds (fur+ vs. fur-).
• To explore the influence of divalent ions and uracil on pyrC expression.

Main Methods:

• Gel retardation assay to assess Fur protein binding to the pyrC promoter region.
• Measurement of dihydroorotase activity in vivo.
• Analysis of beta-galactosidase levels in a pyrC-lacZ fusion system.

Main Results:

• The Fur protein binds to the promoter region of the pyrC gene.
• pyrC expression was significantly repressed (to 30% and 17%) in a fur+ background compared to a fur- background.
• Repression by Fur was not dependent on Fe2+ or Zn2+; uracil independently reduced pyrC expression by half.

Conclusions:

• The Fur protein acts as a repressor of pyrC gene expression in Escherichia coli.
• This regulation is independent of divalent metal ions typically associated with Fur function.
• Uracil also modulates pyrC expression through a mechanism distinct from Fur-mediated regulation.