Abstract
ATP-binding cassette (ABC) transporters, a superfamily of integral membrane proteins, catalyse the translocation of substrates across the cellular membrane by ATP hydrolysis. Here we demonstrate by nucleotide turnover and binding studies based on 31P solid-state NMR spectroscopy that the ABC exporter and lipid A flippase MsbA can couple ATP hydrolysis to an adenylate kinase activity, where ADP is converted into AMP and ATP. Single-point mutations reveal that both ATPase and adenylate kinase mechanisms are associated with the same conserved motifs of the nucleotide-binding domain. Based on these results, we propose a model for the coupled ATPase-adenylate kinase mechanism, involving the canonical and an additional nucleotide-binding site. We extend these findings to other prokaryotic ABC exporters, namely LmrA and TmrAB, suggesting that the coupled activities are a general feature of ABC exporters.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ATP-Binding Cassette Transporters / chemistry
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ATP-Binding Cassette Transporters / genetics
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ATP-Binding Cassette Transporters / metabolism*
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Adenosine Triphosphatases / chemistry
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / metabolism
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Adenosine Triphosphate / metabolism
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Adenylate Kinase / chemistry
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Adenylate Kinase / genetics
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Adenylate Kinase / metabolism
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Amino Acid Substitution
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Bacterial Proteins / chemistry
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism*
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Binding Sites / genetics
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Escherichia coli Proteins / chemistry
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Escherichia coli Proteins / genetics
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Escherichia coli Proteins / metabolism*
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Humans
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Magnetic Resonance Spectroscopy
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Models, Biological
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Models, Molecular
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Mutagenesis, Site-Directed
Substances
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ATP-Binding Cassette Transporters
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Bacterial Proteins
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Escherichia coli Proteins
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MsbA protein, Bacteria
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Adenosine Triphosphate
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Adenylate Kinase
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Adenosine Triphosphatases