Resting state conformation of the MsbA homodimer as studied by site-directed spin labeling. Biochemistry 2004 Jul 06;43(26):8600-6
Date
06/30/2004Pubmed ID
15222771DOI
10.1021/bi0497751Scopus ID
2-s2.0-3142580842 (requires institutional sign-in at Scopus site) 33 CitationsAbstract
MsbA is the ABC transporter for lipid A and is found in the inner membranes of Gram-negative bacteria such as Escherichia coli. Without MsbA present, bacterial cells accumulate a toxic amount of lipid A within their inner membranes. A crystal structure of MsbA was recently obtained that provides an excellent starting point for functional dynamics studies in membranes [Chang, and Roth (2001) Science 293, 1793-1800]. Although a structure of MsbA is now available, many questions remain concerning its mechanism of transport. Site-directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy is a powerful approach for characterizing local areas within a large protein structure in addition to detecting and following changes in local structure due to dynamic interactions within a protein. The quaternary structure of the resting state of the MsbA homodimer reconstituted into lipid membranes has been evaluated by SDSL EPR spectroscopy and chemical cross-linking techniques. SDSL and cross-linking results are consistent with the controversial resting state conformation of the MsbA homodimer found in the crystal structure, with the tips of the transmembrane helices forming a dimer interface. The position of MsbA in the membrane bilayer along with the relative orientation of the transmembrane helical bundles with respect to one another has been determined. Characterization of the resting state of the MsbA homodimer is essential for future studies on the functional dynamics of this membrane transporter.
Author List
Buchaklian AH, Funk AL, Klug CSAuthor
Candice S. Klug PhD Professor in the Biophysics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
ATP-Binding Cassette TransportersBacterial Proteins
Biological Transport
Cross-Linking Reagents
Crystallography, X-Ray
Cysteine
Dimerization
Electron Spin Resonance Spectroscopy
Escherichia coli
Kinetics
Lipid Metabolism
Models, Molecular
Mutagenesis, Site-Directed
Mutation
Plasmids
Protein Conformation
Protein Structure, Quaternary