SirR, a novel iron-dependent repressor in Staphylococcus epidermidis

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Iron starvation induces lipoproteins in Staphylococcus epidermidis and Staphylococcus aureus.
• Iron-dependent gene regulation in staphylococci is not fully understood.

Purpose of the Study:

• To investigate the molecular mechanisms of iron-dependent gene regulation in staphylococci.
• To identify and characterize the transcriptional regulator of the S. epidermidis sitABC operon.

Main Methods:

• DNA sequencing upstream of the S. epidermidis sitABC operon.
• Identification of homologous sequences to Corynebacterium diphtheriae DtxR regulon elements.
• Overexpression and purification of the putative repressor protein SirR.
• DNA mobility shift assays to determine SirR-binding activity.
• Southern blot analysis to assess the prevalence of SirR-binding sites.
• Western blot analysis to detect SirR protein across staphylococcal species.

Main Results:

• A novel gene, SirR (staphylococcal iron regulator repressor), was identified upstream of the sitABC operon.
• SirR exhibits homology to DtxR family metal-dependent repressor proteins.
• A SirR-binding site, the 'Sir box', was identified in the sitABC promoter region.
• SirR binding to the Sir box is dependent on divalent metal cations (Fe2+ or Mn2+).
• SirR-binding sites (Sir boxes) are present in multiple staphylococcal genomes, suggesting regulation of multiple genes.
• SirR protein is conserved across various staphylococcal species.

Conclusions:

• SirR functions as a divalent metal cation-dependent transcriptional repressor in staphylococci.
• SirR plays a significant role in iron homeostasis and gene regulation within the staphylococci.
• The SirR regulatory system is conserved and widespread among staphylococcal species.