title: Structural basis for sensory rhodopsin function.
abstract: The crystal structure of sensory rhodopsin II from Natronobacterium pharaonis was recently solved at 2.1 A resolution from lipidic cubic phase-grown crystals. A critical analysis of previous structure-function studies is possible within the framework of the high-resolution structure of this photoreceptor. Based on the structure, a molecular understanding emerges of the efficiency and selectivity of the photoisomerization reaction, of the interaction of the sensory receptor and its cognate transducer protein HtrII, and of the mechanism of spectral tuning in photoreceptors. The architecture of the retinal binding pocket is compact, representing a major determinant for the selective binding of the chromophore, all-trans retinal to the apoprotein, opsin. Several chromophore-protein interactions revealed by the structure were not predicted by previous mutagenesis and spectroscopic analyses. The structure suggests likely mechanisms by which photoisomerization triggers the activation of sensory rhodopsin II, and highlights the possibility of a unified mechanism of signaling mediated by sensory receptors, including visual rhodopsins. Future investigations using time-resolved crystallography, structural dynamics, and computational studies will provide the basis to unveil the molecular mechanisms of sensory receptors-mediated transmembrane signaling.
authors.affiliation: Institut de Biologie Structurale, UMR5075, CEA-CNRS-Université Joseph Fourier, 41 rue Jules Horowitz, Grenoble, France.
authors.forename: Eva
authors.initials: E
authors.lastname: Pebay-Peyroula
authors.forename: Antoine
authors.initials: A
authors.lastname: Royant
authors.forename: Ehud M
authors.initials: EM
authors.lastname: Landau
authors.forename: Javier
authors.initials: J
authors.lastname: Navarro
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000502:physiology; D001665:Binding Sites; D002338:Carotenoids / Q000737:chemistry; D003461:Crystallography; D003593:Cytoplasm / Q000737:chemistry; D025602:Halorhodopsins; D008565:Membrane Proteins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019633:Natronobacterium / Q000737:chemistry* / Q000502:physiology; D012172:Retinaldehyde / Q000737:chemistry; D025603:Sensory Rhodopsins / Q000737:chemistry* / Q000502:physiology; D015398:Signal Transduction; D013053:Spectrophotometry; D013329:Structure-Activity Relationship
chemical_list: D019843:Archaeal Proteins; D025602:Halorhodopsins; C434451:HtrII protein, Natronobacterium pharaonis; D008565:Membrane Proteins; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal; D002338:Carotenoids; D012172:Retinaldehyde