title: A NarX-Tar chimera mediates repellent chemotaxis to nitrate and nitrite.
abstract: Membrane receptors communicate between the external world and the cell interior. In bacteria, these receptors include the transmembrane sensor kinases, which control gene expression via their cognate response regulators, and chemoreceptors, which control the direction of flagellar rotation via the CheA kinase and CheY response regulator. Here, we show that a chimeric protein that joins the ligand-binding, transmembrane and linker domains of the NarX sensor kinase to the signalling and adaptation domains of the Tar chemoreceptor of Escherichia coli mediates repellent responses to nitrate and nitrite. Nitrate induces a stronger response than nitrite and is effective at lower concentrations, mirroring the relative sensitivity to these ligands exhibited by NarX itself. We conclude that the NarX-Tar hybrid functions as a bona fide chemoreceptor whose activity can be predicted from its component parts. This observation implies that ligand-dependent activation of a sensor kinase and repellent-initiated activation of receptor-coupled CheA kinase involve a similar transmembrane signal.
authors: Department of Biology, Texas A and M University, College Station 77843, USA.
authors: Scott M
authors: SM
authors: Ward
authors: Asuncion
authors: A
authors: Delgado
authors: Robert P
authors: RP
authors: Gunsalus
authors: Michael D
authors: MD
authors: Manson
mesh_terms: D001426:Bacterial Proteins; D001431:Bacteriological Techniques / Q000295:instrumentation; D018914:Cells, Immobilized; D002628:Chemoreceptor Cells; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology*; D004058:Diffusion; D004789:Enzyme Activation; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology*; D000071677:Histidine Kinase; D008024:Ligands; D008565:Membrane Proteins / Q000502:physiology; D000072236:Methyl-Accepting Chemotaxis Proteins; D008958:Models, Molecular; D009566:Nitrates / Q000494:pharmacology*; D009573:Nitrites / Q000494:pharmacology*; D009994:Osmolar Concentration; D010766:Phosphorylation; D011487:Protein Conformation; D011494:Protein Kinases / Q000235:genetics / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008024:Ligands; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D009566:Nitrates; D009573:Nitrites; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; C057331:Tar protein, E coli; C000607606:cheY protein, E coli; D011494:Protein Kinases; D000071677:Histidine Kinase; C000607608:cheA protein, E coli; C074787:narX protein, E coli