title: Crystal structure of a catalytic intermediate of the maltose transporter.
abstract: The maltose uptake system of Escherichia coli is a well-characterized member of the ATP-binding cassette transporter superfamily. Here we present the 2.8-A crystal structure of the intact maltose transporter in complex with the maltose-binding protein, maltose and ATP. This structure, stabilized by a mutation that prevents ATP hydrolysis, captures the ATP-binding cassette dimer in a closed, ATP-bound conformation. Maltose is occluded within a solvent-filled cavity at the interface of the two transmembrane subunits, about halfway into the lipid bilayer. The binding protein docks onto the entrance of the cavity in an open conformation and serves as a cap to ensure unidirectional translocation of the sugar molecule. These results provide direct evidence for a concerted mechanism of transport in which solute is transferred from the binding protein to the transmembrane subunits when the cassette dimer closes to hydrolyse ATP.
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Oldham
authors.forename: Dheeraj
authors.initials: D
authors.lastname: Khare
authors.forename: Florante A
authors.initials: FA
authors.lastname: Quiocho
authors.forename: Amy L
authors.initials: AL
authors.lastname: Davidson
authors.forename: Jue
authors.initials: J
authors.lastname: Chen
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002384:Catalysis; D002462:Cell Membrane / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006868:Hydrolysis; D008320:Maltose / Q000378:metabolism*; D058619:Maltose-Binding Proteins; D008954:Models, Biological; D008958:Models, Molecular; D009004:Monosaccharide Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011487:Protein Conformation
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C461639:MalF protein, E coli; C079123:MalG protein, E coli; C489398:MalK protein, E coli; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D046912:Multiprotein Complexes; D008320:Maltose; D000255:Adenosine Triphosphate