A multidrug ABC transporter with a taste for salt
Saroj Velamakanni1, Calvin H F Lau, Daniel A P Gutmann
1Department of Pharmacology, University of Cambridge, Cambridge, UK.
Plos One
|July 14, 2009
Summary
The Lactococcus lactis multidrug transporter LmrA facilitates secondary-active transport of NaCl, enhancing bacterial survival during salt stress. This study reveals a novel link between LmrA activity and ion transport mechanisms.
Area of Science:
- Biochemistry
- Molecular Biology
- Microbiology
Background:
- LmrA from Lactococcus lactis is a multidrug ATP-binding cassette (ABC) transporter with a broad substrate range.
- It can functionally substitute for human ABCB1 (P-glycoprotein) and utilizes proton-motive force for secondary-active transport.
- The precise mechanism and physiological role of LmrA's H(+)-coupled transport remain unclear.
Purpose of the Study:
- To investigate the ion transport capabilities of the LmrA transporter.
- To elucidate the mechanism and physiological relevance of LmrA-mediated ion transport.
- To explore the potential role of LmrA in cellular response to ionic stress.
Main Methods:
- Electrophysiological experiments were conducted to study ion transport.
- Transport assays utilized radioactive ions and fluorescent ion-selective probes.
- Lactococcal cell survival under ionic stress was assessed in relation to LmrA activity.
Main Results:
- LmrA was shown to transport NaCl via a secondary-active mechanism, exhibiting apparent H(+)-Na(+)-Cl(-) symport.
- LmrA activity was found to significantly improve the survival of salt-adapted Lactococcus lactis cells during ionic downshift.
- This study marks the first application of electrophysiology to analyze substrate transport by a purified multidrug transporter.
Conclusions:
- The findings confirm H(+)-coupled transport by LmrA and establish a novel connection between its activity and salt stress response.
- Investigating the bioenergetics of substrate translocation in ABC transporters is crucial for understanding fundamental mechanisms.
- This research provides new insights into the functional diversity of ABC transporters and their roles in cellular homeostasis.
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