title: Functionally important ATP binding and hydrolysis sites in Escherichia coli MsbA.
abstract: ATP-binding cassette (ABC) transporters make up one of the largest classes of proteins found in nature, and their ability to move a variety of substrates across the membrane using energy from the binding or hydrolysis of ATP is essential to an array of human pathologies and to bacterial viability. MsbA is an essential ABC transporter that specifically transports lipid A across the inner membranes of Gram-negative organisms such as Escherichia coli. The exact mechanisms of function during the binding and hydrolysis of ATP at the molecular level remain unclear. The studies presented and summarized in this work directly address the role and local dynamics of specific residues within the conserved ABC motifs in E. coli MsbA using in vivo growth and biochemical activity assays coupled with site-directed spin labeling electron paramagnetic resonance (EPR) spectroscopy motional and accessibility analysis. This first comprehensive analysis of the specific residues in these motifs within MsbA indicates that closure of the dimer interface does not occur upon ATP binding in this transporter.
authors.affiliation: Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Westfahl
authors.forename: Jacqueline A
authors.initials: JA
authors.lastname: Merten
authors.forename: Adam H
authors.initials: AH
authors.lastname: Buchaklian
authors.forename: Candice S
authors.initials: CS
authors.lastname: Klug
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D017124:Conserved Sequence; D019281:Dimerization; D004578:Electron Spin Resonance Spectroscopy; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D006868:Hydrolysis; D008050:Lipid A / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008050:Lipid A; C079726:MsbA protein, Bacteria; D000255:Adenosine Triphosphate