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Functionally important ATP binding and hydrolysis sites in Escherichia coli MsbA
Kathryn M Westfahl1, Jacqueline A Merten, Adam H Buchaklian
1Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA.
Biochemistry
|December 5, 2008
Summary
This study investigates the essential bacterial transporter MsbA in E. coli. Researchers found that ATP binding does not cause the MsbA dimer interface to close, clarifying transporter function.
Area of Science:
- Biochemistry
- Molecular Biology
- Microbiology
Background:
- ATP-binding cassette (ABC) transporters are crucial for moving substrates across membranes, impacting human diseases and bacterial survival.
- MsbA is an essential ABC transporter in Gram-negative bacteria like E. coli, responsible for transporting lipid A across the inner membrane.
- The precise molecular mechanisms of ATP binding and hydrolysis in ABC transporters, including MsbA, are not fully understood.
Purpose of the Study:
- To elucidate the role and dynamics of specific residues within the conserved ABC motifs of E. coli MsbA.
- To investigate the conformational changes associated with ATP binding and hydrolysis in MsbA at a molecular level.
Main Methods:
- Utilized in vivo growth assays and biochemical activity assays.
- Employed site-directed spin labeling electron paramagnetic resonance (EPR) spectroscopy for motional and accessibility analysis.
- Focused on specific residues within the conserved ABC motifs of E. coli MsbA.
Main Results:
- Provided the first comprehensive analysis of specific residues within MsbA's ABC motifs.
- Demonstrated that ATP binding to MsbA does not induce closure of the dimer interface.
- Characterized the local dynamics and accessibility of key residues during transporter function.
Conclusions:
- The findings challenge the model of dimer interface closure upon ATP binding for MsbA.
- Offers new insights into the mechanism of ATP-dependent transport in essential bacterial ABC transporters.
- Highlights the utility of EPR spectroscopy in studying transporter dynamics.
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