title: Both maltose-binding protein and ATP are required for nucleotide-binding domain closure in the intact maltose ABC transporter.
abstract: The maltose transporter MalFGK(2) of Escherichia coli is a member of the ATP-binding cassette superfamily. A periplasmic maltose-binding protein (MBP) delivers maltose to MalFGK(2) and stimulates its ATPase activity. Site-directed spin labeling EPR spectroscopy was used to study the opening and closing of the nucleotide-binding interface of MalFGK(2) during the catalytic cycle. In the intact transporter, closure of the interface coincides not just with the binding of ATP, as seen with isolated nucleotide-binding domains, but requires both MBP and ATP, implying that MBP stimulates ATPase activity by promoting the closure of the nucleotide-binding interface. After ATP hydrolysis, with MgADP and MBP bound, the nucleotide-binding interface resides in a semi-open configuration distinct from the fully open configuration seen in the absence of any ligand. We propose that P(i) release coincides with the reorientation of transmembrane helices to an inward-facing conformation and the final step of maltose translocation into the cell.
authors: Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907, USA.
authors: Cedric
authors: C
authors: Orelle
authors: Tulin
authors: T
authors: Ayvaz
authors: R Michael
authors: RM
authors: Everly
authors: Candice S
authors: CS
authors: Klug
authors: Amy L
authors: AL
authors: Davidson
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism* / Q000494:pharmacology; D002384:Catalysis / Q000187:drug effects; D019281:Dimerization; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D008024:Ligands; D008081:Liposomes / Q000378:metabolism; D008320:Maltose / Q000378:metabolism; D058619:Maltose-Binding Proteins; D008958:Models, Molecular; D009004:Monosaccharide Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013113:Spin Labels
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D008024:Ligands; D008081:Liposomes; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D050505:Mutant Proteins; D013113:Spin Labels; C461599:maltose transport system, E coli; D000266:Adenylyl Imidodiphosphate; D008320:Maltose; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases