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A putative multisubunit Na+/H+ antiporter from Staphylococcus aureus
T Hiramatsu1, K Kodama, T Kuroda
1Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Tsushima, Okayama 700-8530, Japan.
Journal of Bacteriology
|December 16, 1998
Summary
Researchers identified a novel seven-subunit Na+/H+ antiporter from Staphylococcus aureus. This bacterial antiporter system, encoded by an operon, facilitates sodium extrusion and alkaline tolerance in Escherichia coli.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Sodium-proton (Na+/H+) antiporters are crucial for maintaining ion homeostasis in bacteria.
- Understanding the diversity and mechanisms of these antiporters is essential for microbial physiology.
- Staphylococcus aureus possesses uncharacterized systems for ion transport.
Purpose of the Study:
- To clone and characterize Na+/H+ antiporter genes from Staphylococcus aureus.
- To investigate the functional properties and subunit composition of the identified antiporter.
- To explore the potential applications of this antiporter system.
Main Methods:
- Cloning of Staphylococcus aureus genes into an Escherichia coli mutant host lacking native antiporters.
- Functional complementation assays assessing growth in high salt (NaCl) and lithium chloride (LiCl) conditions.
- Measurement of Na+/H+ antiport activity in membrane vesicles.
- Nucleotide sequencing of the cloned DNA region and analysis of open reading frames (ORFs).
- Hydropathy analysis and homology searches of deduced amino acid sequences.
- Respiration-driven sodium extrusion assays and sensitivity testing with H+ conductors.
Main Results:
- Seven open reading frames (ORFs) comprising a potential operon were identified and found essential for Na+/H+ antiporter function.
- The cloned genes conferred the ability to grow in 0.2 M NaCl or 10 mM LiCl to the E. coli host.
- Functional Na+/H+ antiport activity and respiration-driven Na+ extrusion were observed in transformants.
- Sequence analysis revealed hydrophobic proteins with homology to respiratory chain components, suggesting a novel multisubunit antiporter structure.
- The system enabled E. coli mutants to grow under alkaline conditions.
Conclusions:
- A novel, seven-subunit Na+/H+ antiporter from Staphylococcus aureus has been identified and functionally characterized.
- This multisubunit antiporter system is encoded by an operon and plays a role in sodium extrusion and alkaline tolerance.
- The findings suggest a unique mechanism for ion transport in bacteria, potentially linked to respiration.