Recombinant Staphylococcus epidermidis Probable quinol oxidase subunit 4 (qoxD)

Biochemical Characteristics and Production

Recombinant qoxD is produced via heterologous expression in Escherichia coli, typically fused with an N-terminal His-tag for purification. Key specifications include:

The amino acid sequence (Q8CPP9) includes conserved motifs for quinol binding and electron transfer, aligning with its role in the cytochrome bc1 complex or terminal oxidases .

Functional Role in S. epidermidis Metabolism

Quinol oxidases catalyze the oxidation of quinols to quinones, transferring electrons to oxygen in the bacterial electron transport chain (ETC). In S. epidermidis, this process is regulated by transcription factors like SrrAB, which modulates genes involved in cytochrome and quinol-oxidase assembly under microaerobic conditions .

Key Functions of Quinol Oxidase Complexes

• Energy Production: Generates ATP via proton translocation during electron transfer.

• Oxygen Tolerance: Enables survival under varying oxygen levels, critical for biofilm formation and host colonization.

• Redox Balance: Maintains intracellular redox states to prevent oxidative stress.

While qoxD specifically is not extensively studied, related subunits (e.g., qoxA, qoxB) are implicated in:

• Electron Transport Efficiency: Regulated by SrrAB under microaerobic conditions .

• Biofilm Formation: Downregulation of qoxB in srrA mutants correlates with reduced polysaccharide intercellular adhesion (PIA) and adherence .

Research Applications and Experimental Insights

Recombinant qoxD is primarily used in:

Immunoassays (e.g., ELISA)

• Antibody Detection: ELISA kits incorporating recombinant qoxD enable detection of anti-S. epidermidis antibodies, aiding in studies of host-pathogen interactions .

• Protein Interaction Studies: His-tagged qoxD facilitates purification for co-immunoprecipitation or surface plasmon resonance assays to map binding partners.

Genomic and Evolutionary Context

S. epidermidis genomes exhibit open pan-genomes with frequent horizontal gene transfer (HGT), enabling acquisition of virulence and antibiotic resistance genes . While qoxD is not directly linked to pathogenicity, its regulation by SrrAB suggests a role in adapting to host niches:

Comparative Analysis with Other Quinol Oxidase Subunits

While qoxD is less characterized, its homologs in S. epidermidis include:

Challenges and Future Directions

• Limited Functional Data: Direct studies on qoxD are sparse; inferences rely on homologs like qoxA/B.

• Pathogenicity Links: No direct evidence ties qoxD to virulence, but its role in ETC efficiency may indirectly support persistence in host niches .

• Therapeutic Targets: Inhibiting quinol oxidase could disrupt metabolic flexibility, though off-target effects in commensal S. epidermidis pose challenges .