Both maltose-binding protein and ATP are required for nucleotide-binding domain closure in the intact maltose ABC transporter

• Published in: Proceedings of the National Academy of Sciences - PNAS 2008-09, Vol.105 (35), p.12837-12842
• Main Authors: Orelle, Cedric, Ayvaz, Tulin, Everly, R. Michael, Klug, Candice S, Davidson, Amy L
• Format: Article
• Language: English
• Subjects: Adenosine triphosphatase; Adenosine triphosphatases; Adenosine Triphosphatases - metabolism; Adenosine Triphosphate - metabolism; Adenosine Triphosphate - pharmacology; Adenylyl Imidodiphosphate - pharmacology; ATP binding cassette transporters; ATP-Binding Cassette Transporters - chemistry; ATP-Binding Cassette Transporters - metabolism; Bacterial proteins; Binding Sites; Biological Sciences; Carrier Proteins - metabolism; Carrier Proteins - pharmacology; Catalysis - drug effects; Dimerization; Dimers; E coli; Electron Spin Resonance Spectroscopy; Escherichia coli; Escherichia coli - metabolism; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - metabolism; Hydrolysis; Ligands; Liposomes - metabolism; Maltose - metabolism; Maltose-Binding Proteins; Models, Molecular; Monosaccharide Transport Proteins - chemistry; Monosaccharide Transport Proteins - metabolism; Mutant Proteins - metabolism; Nucleotides; Protein Structure, Tertiary; Signatures; Spectral index; Spectroscopy; Spectrum analysis; Spin Labels; Sugar
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0803799105

The maltose transporter MalFGK₂ of Escherichia coli is a member of the ATP-binding cassette superfamily. A periplasmic maltose-binding protein (MBP) delivers maltose to MalFGK₂ 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 MalFGK₂ 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 Pi release coincides with the reorientation of transmembrane helices to an inward-facing conformation and the final step of maltose translocation into the cell.