title: Active state of sensory rhodopsin II: structural determinants for signal transfer and proton pumping.
abstract: The molecular mechanism of transmembrane signal transduction is still a pertinent question in cellular biology. Generally, a receptor can transfer an external signal via its cytoplasmic surface, as found for G-protein-coupled receptors such as rhodopsin, or via the membrane domain, such as that in sensory rhodopsin II (SRII) in complex with its transducer, HtrII. In the absence of HtrII, SRII functions as a proton pump. Here, we report on the crystal structure of the active state of uncomplexed SRII from Natronomonas pharaonis, NpSRII. The problem with a dramatic loss of diffraction quality upon loading of the active state was overcome by growing better crystals and by reducing the occupancy of the state. The conformational changes in the region comprising helices F and G are similar to those observed for the NpSRII-transducer complex but are much more pronounced. The meaning of these differences for the understanding of proton pumping and signal transduction by NpSRII is discussed.
authors.affiliation: Laboratoire des Protéines Membranaires, Institut de Biologie Structurale J.-P. Ebel, UMR5075 CEA-CNRS-UJF, 38027 Grenoble, France.
authors.forename: Ivan
authors.initials: I
authors.lastname: Gushchin
authors.forename: Anastasia
authors.initials: A
authors.lastname: Reshetnyak
authors.forename: Valentin
authors.initials: V
authors.lastname: Borshchevskiy
authors.forename: Andrii
authors.initials: A
authors.lastname: Ishchenko
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Round
authors.forename: Sergei
authors.initials: S
authors.lastname: Grudinin
authors.forename: Martin
authors.initials: M
authors.lastname: Engelhard
authors.forename: Georg
authors.initials: G
authors.lastname: Büldt
authors.forename: Valentin
authors.initials: V
authors.lastname: Gordeliy
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism*; D002338:Carotenoids / Q000737:chemistry* / Q000378:metabolism*; D003460:Crystallization; D018360:Crystallography, X-Ray; D006216:Halobacteriaceae / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D019633:Natronobacterium / Q000737:chemistry; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D017494:Proton Pumps / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D025603:Sensory Rhodopsins / Q000737:chemistry* / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
chemical_list: D019843:Archaeal Proteins; D017494:Proton Pumps; D025603:Sensory Rhodopsins; C434450:phototaxis receptor sensory rhodopsin II, Natronobacterium pharaonis; D002338:Carotenoids