title: Axial helix rotation as a mechanism for signal regulation inferred from the crystallographic analysis of the E. coli serine chemoreceptor.
abstract: Bacterial chemotaxis receptors are elongated homodimeric coiled-coil bundles, which transduce signals generated in an N-terminal sensor domain across 15-20nm to a conserved C-terminal signaling subdomain. This signal transduction regulates the activity of associated kinases, altering the behavior of the flagellar motor and hence cell motility. Signaling is in turn modulated by selective methylation and demethylation of specific glutamate and glutamine residues in an adaptation subdomain. We have determined the structure of a chimeric protein, consisting of the HAMP domain from Archaeoglobus fulgidus Af1503 and the methyl-accepting domain of Escherichia coli Tsr. It shows a 21nm coiled coil that alternates between two coiled-coil packing modes: canonical knobs-into-holes and complementary x-da, a variant form related to the canonical one by axial rotation of the helices. Comparison of the obtained structure to the Thermotoga maritima chemoreceptor TM1143 reveals that they adopt different axial rotation states in their adaptation subdomains. This conformational change is presumably induced by the upstream HAMP domain and may modulate the affinity of the chemoreceptor to the methylation-demethylation system. The presented findings extend the cogwheel model for signal transmission to chemoreceptors.
authors.affiliation: Department of Protein Evolution, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.
authors.forename: Hedda U
authors.initials: HU
authors.lastname: Ferris
authors.affiliation: Department of Protein Evolution, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.
authors.forename: Kornelius
authors.initials: K
authors.lastname: Zeth
authors.affiliation: Department of Protein Evolution, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hulko
authors.affiliation: Department of Protein Evolution, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.
authors.forename: Stanislaw
authors.initials: S
authors.lastname: Dunin-Horkawicz
authors.affiliation: Department of Protein Evolution, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany. Electronic address: andrei.lupas@tuebingen.mpg.de.
authors.forename: Andrei N
authors.initials: AN
authors.lastname: Lupas
mesh_terms: D000595:Amino Acid Sequence; D019611:Archaeoglobus fulgidus / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000072236:Methyl-Accepting Chemotaxis Proteins; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D020124:Thermotoga maritima / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D011993:Recombinant Fusion Proteins; C000607604:tsr protein, E coli
keywords: Bacterial signal transduction; Chemoreceptor; Chemotaxis; Coiled coil; HAMP domain