Recombinant Staphylococcus epidermidis Probable quinol oxidase subunit 2 (qoxA)

Gene and Protein Information

• Gene Name: qoxA (SE_0759 in some strains)

• Synonyms: Quinol oxidase polypeptide II, Probable quinol oxidase subunit 2 .

• UniProt IDs: Q5HQA9 (full-length) , Q8CPP6 (partial) , Q8CMQ2 (partial) .

• Sequence Length:

  • Full-length: 355 amino acids (20-374 aa) .

  • Partial: 189 amino acids (1-189 aa) .

The protein contains a His-tag (N-terminal in recombinant versions) and shares structural homology with quinol oxidase subunits in other Gram-positive bacteria.

Biochemical Properties

Expression Systems and Tags

Recombinant qoxA is produced in:

• E. coli: Full-length protein with N-terminal His-tag .

• Yeast: Partial-length protein (e.g., 1-189 aa) .

Quinol Oxidase Activity

qoxA is a subunit of a cytochrome bd-type quinol oxidase, which catalyzes electron transfer from quinols to oxygen in the ETC . This enzyme is critical for:

• Aerobic respiration: Under oxic conditions, it supports bacterial growth and biofilm formation .

• Oxygen adaptation: Regulated by the SrrAB two-component system, which modulates qoxBACD operon expression (including qoxA) in response to oxygen levels .

Regulation and Biofilm Formation

• SrrAB dependency: SrrAB upregulates qoxBACD under oxic conditions, linking qoxA expression to electron transport efficiency and biofilm maturation .

• Metabolic adaptation: qoxA activity is coupled with fermentation pathways (e.g., pflBA) under microaerobic conditions, enabling survival in diverse niches .

Diagnostic and Analytical Tools

• ELISA kits: Recombinant qoxA is used as an antigen to detect anti-S. epidermidis antibodies .

• Western blotting: Validates protein expression in S. epidermidis mutants or clinical isolates .

Functional Studies

• Biofilm regulation: qoxA knockout models investigate its role in oxygen-dependent biofilm formation .

• Protein-protein interactions: Studies explore SrrAB binding to qoxA promoter regions .

Oxygen-Dependent Regulation

• Oxic conditions: SrrAB activates qoxBACD (including qoxA) to enhance ETC activity and biofilm production .

• Microaerobic conditions: SrrAB downregulates qoxA while upregulating fermentation genes (e.g., pflBA) .

Clinical Relevance

• Pathogenicity: qoxA is expressed in both commensal and pathogenic S. epidermidis strains, though its role in virulence remains unclear .

• Antibiotic resistance: Horizontal gene transfer of mecA (methicillin resistance) in S. epidermidis populations may intersect with qoxA-related metabolic pathways .