title: Conformational motion of the ABC transporter MsbA induced by ATP hydrolysis.
abstract: We measured the amplitude of conformational motion in the ATP-binding cassette (ABC) transporter MsbA upon lipopolysaccharide (LPS) binding and following ATP turnover by pulse double electron-electron resonance and fluorescence homotransfer. The distance constraints from both methods reveal large-scale movement of opposite signs in the periplasmic and cytoplasmic part of the transporter upon ATP hydrolysis. LPS induces distinct structural changes that are inhibited by trapping of the transporter in an ATP post-hydrolysis intermediate. The formation of this intermediate involves a 33-A distance change between the two ABCs, which is consistent with a dimerization-dissociation cycle during transport that leads to their substantial separation in the absence of nucleotides. Our results suggest that ATP-powered transport entails LPS sequestering into the open cytoplasmic chamber prior to its translocation by alternating access of the chamber, made possible by 10-20-A conformational changes.
authors.affiliation: Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York, United States of America.
authors.forename: Peter P
authors.initials: PP
authors.lastname: Borbat
authors.forename: Kavitha
authors.initials: K
authors.lastname: Surendhran
authors.forename: Marco
authors.initials: M
authors.lastname: Bortolus
authors.forename: Ping
authors.initials: P
authors.lastname: Zou
authors.forename: Jack H
authors.initials: JH
authors.lastname: Freed
authors.forename: Hassane S
authors.initials: HS
authors.lastname: Mchaourab
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D004734:Energy Metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D005454:Fluorescence Polarization; D006868:Hydrolysis; D008070:Lipopolysaccharides / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D011485:Protein Binding; D011487:Protein Conformation; D013113:Spin Labels
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008070:Lipopolysaccharides; C079726:MsbA protein, Bacteria; D013113:Spin Labels; D000255:Adenosine Triphosphate