title: Photocyclic behavior of rhodopsin induced by an atypical isomerization mechanism.
abstract: Vertebrate rhodopsin (Rh) contains 11-cis-retinal as a chromophore to convert light energy into visual signals. On absorption of light, 11-cis-retinal is isomerized to all-trans-retinal, constituting a one-way reaction that activates transducin (Gt) followed by chromophore release. Here we report that bovine Rh, regenerated instead with a six-carbon-ring retinal chromophore featuring a C11=C12double bond locked in itscisconformation (Rh6mr), employs an atypical isomerization mechanism by converting 11-cisto an 11,13-dicisconfiguration for prolonged Gtactivation. Time-dependent UV-vis spectroscopy, HPLC, and molecular mechanics analyses revealed an atypical thermal reisomerization of the 11,13-dicisto the 11-cisconfiguration on a slow timescale, which enables Rh6mr to function in a photocyclic manner similar to that of microbial Rhs. With this photocyclic behavior, Rh6mr repeatedly recruits and activates Gtin response to light stimuli, making it an excellent candidate for optogenetic tools based on retinal analog-bound vertebrate Rhs. Overall, these comprehensive structure-function studies unveil a unique photocyclic mechanism of Rh activation by an 11-cis-to-11,13-dicisisomerization.
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106.|Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, OH 44106.
authors.forename: Sahil
authors.initials: S
authors.lastname: Gulati
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106.|Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, OH 44106.
authors.forename: Beata
authors.initials: B
authors.lastname: Jastrzebska
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14850.|Northeastern Collaborative Access Team, Argonne National Laboratory, Argonne, IL 60439.
authors.forename: Surajit
authors.initials: S
authors.lastname: Banerjee
authors.affiliation: Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106.
authors.forename: Ángel L
authors.initials: ÁL
authors.lastname: Placeres
authors.affiliation: Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, 00-927 Warsaw, Poland.
authors.forename: Przemyslaw
authors.initials: P
authors.lastname: Miszta
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106.
authors.forename: Songqi
authors.initials: S
authors.lastname: Gao
authors.affiliation: Novartis Institutes for BioMedical Research, Cambridge, MA 02139.
authors.forename: Karl
authors.initials: K
authors.lastname: Gunderson
authors.affiliation: Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106.
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Tochtrop
authors.affiliation: Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, 00-927 Warsaw, Poland.
authors.forename: Sławomir
authors.identifier: 0000-0003-3147-3858
authors.initials: S
authors.lastname: Filipek
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106; kxk477@case.edu kxp65@case.edu.
authors.forename: Kota
authors.initials: K
authors.lastname: Katayama
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106.|Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH 44106.
authors.forename: Philip D
authors.identifier: 0000-0003-1184-9539
authors.initials: PD
authors.lastname: Kiser
authors.affiliation: Novartis Institutes for BioMedical Research, Cambridge, MA 02139.
authors.forename: Muneto
authors.initials: M
authors.lastname: Mogi
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106.|Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, OH 44106.
authors.forename: Phoebe L
authors.initials: PL
authors.lastname: Stewart
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106; kxk477@case.edu kxp65@case.edu.|Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, OH 44106.
authors.forename: Krzysztof
authors.identifier: 0000-0002-0788-545X
authors.initials: K
authors.lastname: Palczewski
mesh_terms: D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D007536:Isomerism; D055668:Photochemical Processes; D012243:Rhodopsin / Q000737:chemistry* / Q000502:physiology / Q000528:radiation effects
chemical_list: D012243:Rhodopsin
keywords: GPCR; chromophore; isomerization; rhodopsin; vision