title: Transient dissociation of the transducer protein from anabaena sensory rhodopsin concomitant with formation of the M state produced upon photoactivation.
abstract: Anabaena sensory rhodopsin (ASR), a microbial rhodopsin in the cyanobacterium sp. PCC7120, has been suggested to regulate cell processes in a light-quality-dependent manner (color-discrimination) through interaction with a water-soluble transducer protein (Tr). However, light-dependent ASR-Tr interaction changes have yet to be demonstrated. We applied the transient grating (TG) method to investigate protein-protein interaction between ASR with Tr. The molecular diffusion component of the TG signal upon photostimulation of ASR(AT) (ASR with an all-trans retinylidene chromophore) revealed that Tr dissociates from ASR upon formation of the M-intermediate and rebinds to ASR during the decay of M; that is, light induces transient dissociation of ASR and Tr during the photocycle. Further correlating the dissociation of the ASR-Tr pair with the M-intermediate, no transient dissociation was observed after the photoexcitation of the blue-shifted ASR(13C) (ASR with 13-cis, 15-syn chromophore), which does not produce M. This distinction between ASR(AT) and ASR(13C), the two isomeric forms in a color-sensitive equilibrium in ASR, provides a potential mechanism for color-sensitive signaling by ASR.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Oiwake, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Kondoh
authors.forename: Keiichi
authors.initials: K
authors.lastname: Inoue
authors.forename: Jun
authors.initials: J
authors.lastname: Sasaki
authors.forename: John L
authors.initials: JL
authors.lastname: Spudich
authors.forename: Masahide
authors.initials: M
authors.lastname: Terazima
mesh_terms: D017033:Anabaena / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D001436:Bacteriorhodopsins / Q000378:metabolism*; D055668:Photochemical Processes; D011485:Protein Binding; D060066:Protein Interaction Maps; D025603:Sensory Rhodopsins / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D025603:Sensory Rhodopsins; D001436:Bacteriorhodopsins