Attractant binding and signaling in the E. coli aspartate receptor
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1995
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Abstract
The chemoreceptors of the enteric bacteria Escherichia coli allow the organism to monitor its environment and to migrate to more favorable surroundings. This system provides an easily accessible model for ligand reception and transmembrane signal transduction. We have genetically mapped the binding sites for aspartate and Maltose-Binding Protein (MBP) on the aspartate chemoreceptor (Tar) of E. coli. An intragenic complementation system demonstrated that MBP binds to both subunits of the Tar homodimer. Current models invoke either subunit-subunit interactions or conformational shifts within individual subunits as mechanisms for chemoreceptor signaling. Our data indicates that the attractant signal can be propagated through a single subunit of the dimer, therefore favoring the latter model. The signal appears to be transmitted by a shift of the final a-helix of the receptor domain relative to the other helices of the periplasm and/or the membrane.
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