Covalent modification regulates ligand binding to receptor complexes in the chemosensory system of Escherichia coli.
In the Escherichia coli chemosensory pathway, receptor modification mediates adaptation to ligand. Evidence is presented that covalent modification influences ligand binding to receptors in complexes with CheW and the kinase CheA. Kinase inhibition was measured with serine receptor complexes in different modification levels; Ki for serine-mediated inhibition increased 10,000-fold from the lowest to the highest level. Without CheA and CheW, ligand binding is unaffected by covalent modification; thus, the influence of covalent modification is mediated only in the receptor complex, a conclusion supported by an analogy to allosteric enzymes and the observation of cooperative kinase inhibition. Also, the finding that a subsaturating serine concentration accelerates active receptor-kinase complex assembly implies that the assembly/disassembly process may also contribute to kinase regulation.
Li
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Department of Chemistry, University of Massachusetts, Amherst 01003-4510, USA.
Weis
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RM
D000494:Allosteric Regulation; D001426:Bacterial Proteins / Q000378:metabolism; D002633:Chemotaxis / Q000502:physiology*; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins; D000071677:Histidine Kinase; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism; D000072236:Methyl-Accepting Chemotaxis Proteins; D008956:Models, Chemical; D011485:Protein Binding; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction
D001426:Bacterial Proteins; C489103:CheW protein, E coli; D029968:Escherichia coli Proteins; D008024:Ligands; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D047428:Protein Kinase Inhibitors; D011956:Receptors, Cell Surface; C051236:CheW protein, Bacteria; D011494:Protein Kinases; D000071677:Histidine Kinase; C000607608:cheA protein, E coli