title: Analysis of light-induced conformational changes of Natronomonas pharaonis sensory rhodopsin II by time resolved electron paramagnetic resonance spectroscopy.
abstract: The nature and kinetics of the conformational changes leading to the activated state of NpSRII/NpHtrII157 were investigated by time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy in combination with site-directed spin labeling (SDSL) on a series of spin labeled mutants of NpSRII. A structural rearrangement of the cytoplasmic moiety of NpSRII upon light activation was detected (helices B, C, F and G). The increase in distance between helices C and F in the M-trapped state of the complex observed in one double mutant is in line with the notion that an outward movement of helix F occurs upon receptor activation. The data obtained from the NpSRII/NpHtrII157 complex reconstituted in purple membrane lipids are compared with those obtained from the X-ray structure of the late M-state of the complex which shows some discrepancies. The results are discussed in the context also of other biophysical and EPR experimental evidences.
authors.affiliation: Fachbereich Physik, Universität Osnabrück, Osnabrück, Germany.
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: Aliaksei
authors.initials: A
authors.lastname: Krasnaberski
authors.forename: Martin
authors.initials: M
authors.lastname: Engelhard
authors.forename: Heinz-Jürgen
authors.initials: HJ
authors.lastname: Steinhoff
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D006216:Halobacteriaceae / Q000737:chemistry* / Q000235:genetics / Q000528:radiation effects; D025602:Halorhodopsins / Q000737:chemistry* / Q000235:genetics / Q000528:radiation effects; D008027:Light; D008958:Models, Molecular; D046912:Multiprotein Complexes; D016297:Mutagenesis, Site-Directed; D010777:Photochemistry; D011487:Protein Conformation / Q000528:radiation effects; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000528:radiation effects; D025603:Sensory Rhodopsins / Q000737:chemistry* / Q000235:genetics / Q000528:radiation effects
chemical_list: D019843:Archaeal Proteins; D025602:Halorhodopsins; C434451:HtrII protein, Natronobacterium pharaonis; D046912:Multiprotein Complexes; D011994:Recombinant Proteins; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal