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Bacterial sodium ion-coupled energetics
1Mikrobiologisches Institut, Eidgenössische Technische Hochschule, ETH-Zentrum, Zürich, Switzerland.
Antonie Van Leeuwenhoek
|January 1, 1994
Summary
This study investigates two bacterial sodium (Na+) pumps: oxaloacetate decarboxylase and F1Fo ATPase. Researchers identified conserved sequences and characterized Na+ transport mechanisms, revealing insights into bacterial energy conservation.
Area of Science:
- Microbiology and Biochemistry
- Bioenergetics and Membrane Transport
- Enzyme Function and Structure
Background:
- Sodium (Na+) bioenergetics is crucial for many bacteria, linking energy-releasing and energy-consuming reactions across membranes.
- This article focuses on two key Na+ pumps: oxaloacetate decarboxylase from Klebsiella pneumoniae and F1Fo ATPase from Propionigenium modestum.
- Oxaloacetate decarboxylase is vital for citrate fermentation, conserving energy via a Na+ gradient.
Purpose of the Study:
- To characterize the Na+-translocating oxaloacetate decarboxylase and F1Fo ATPase in bacteria.
- To elucidate the molecular mechanisms and sequence features involved in Na+ translocation and energy conservation.
- To investigate the role of these pumps in bacterial growth and ATP synthesis.
Main Methods:
- Gene cloning and sequencing of Na+ pump enzymes.
- Biochemical characterization of enzyme activity and coupling ratios.
- In vivo complementation studies to create hybrid ATPases and assess functionality.
- Site-directed modification studies to identify Na+ binding sites.
Main Results:
- Identified conserved sequence identities in beta-subunits of oxaloacetate decarboxylase, including potential Na+ translocation aspartates.
- Demonstrated that the coupling ratio of decarboxylase Na+ pumps is dependent on the Na+ gradient (delta muNa+).
- Showcased a hybrid F1Fo ATPase conferring Na+-dependent growth on E. coli, highlighting the Fo part's role in ion specificity.
- Pinpointed glutamate-65 in subunit c of P. modestum ATPase as a likely Na+ binding site.
Conclusions:
- Bacterial Na+ pumps, like oxaloacetate decarboxylase and F1Fo ATPase, play critical roles in energy conservation and ATP synthesis.
- Conserved protein structures and specific amino acid residues are essential for Na+ translocation and pump function.
- Understanding these Na+ transport systems provides insights into diverse bacterial metabolic strategies and potential biotechnological applications.