title: Salt-driven equilibrium between two conformations in the HAMP domain from Natronomonas pharaonis: the language of signal transfer?
abstract: HAMP domains (conserved in histidine kinases, adenylyl cyclases, methyl-accepting chemotaxis proteins, and phosphatases) perform their putative function as signal transducing units in diversified environments in a variety of protein families. Here the conformational changes induced by environmental agents, namely salt and temperature, on the structure and function of a HAMP domain of the phototransducer from Natronomonas pharaonis (NpHtrII) in complex with sensory rhodopsin II (NpSRII) were investigated by site-directed spin labeling electron paramagnetic resonance. A series of spin labeled mutants were engineered in NpHtrII157, a truncated analog containing only the first HAMP domain following the transmembrane helix 2. This truncated transducer is shown to be a valid model system for a signal transduction domain anchored to the transmembrane light sensor NpSRII. The HAMP domain is found to be engaged in a "two-state" equilibrium between a highly dynamic (dHAMP) and a more compact (cHAMP) conformation. The structural properties of the cHAMP as proven by mobility, accessibility, and intra-transducer-dimer distance data are in agreement with the four helical bundle NMR model of the HAMP domain from Archaeoglobus fulgidus.
authors.affiliation: Fachbereich Physik, Universität Osnabrück, Barbarastrasse 7, 49076 Osnabrück, Germany.
authors.forename: Meike
authors.initials: M
authors.lastname: Doebber
authors.forename: Enrica
authors.initials: E
authors.lastname: Bordignon
authors.forename: Johann P
authors.initials: JP
authors.lastname: Klare
authors.forename: Julia
authors.initials: J
authors.lastname: Holterhues
authors.forename: Swetlana
authors.initials: S
authors.lastname: Martell
authors.forename: Nadine
authors.initials: N
authors.lastname: Mennes
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.forename: Martin
authors.initials: M
authors.lastname: Engelhard
authors.forename: Heinz-Jürgen
authors.initials: HJ
authors.lastname: Steinhoff
mesh_terms: D000595:Amino Acid Sequence; D004578:Electron Spin Resonance Spectroscopy; D006216:Halobacteriaceae / Q000378:metabolism*; D025602:Halorhodopsins / Q000737:chemistry; D008027:Light; D055537:Light Signal Transduction; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012492:Salts / Q000494:pharmacology*; D025603:Sensory Rhodopsins / Q000737:chemistry; D015398:Signal Transduction
chemical_list: D025602:Halorhodopsins; D012492:Salts; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal