title: A purified agonist-activated G-protein coupled receptor: truncated octopus Acid Metarhodopsin.
abstract: G-protein coupled receptors (GPCRs) mediate responses to many types of extracellular signals. So far, bovine rhodopsin, the inactive form of a GPCR, is the only member of the family whose three dimensional structure has been determined. It would be desirable to determine the structure of the active form of a GPCR. In this paper, we report the large scale preparation of a stable, homogenous species, truncated octopus rhodopsin (t-rhodopsin) in which proteolysis has removed the proline-rich C-terminal; this species retains the spectral properties and the ability for light-induced G-protein activation of unproteolyzed octopus rhodopsin. Moreover, starting from this species we can prepare a pure, active form of pigment, octopus t-Acid Metarhodopsin which has an all-trans-retinal as its agonist. Photoisomerization of t-Acid Metarhodopsin leads back to the inactive form, t-rhodopsin with the inverse agonist 11-cis-retinal. Octopus t-Acid Metarhodopsin can activate an endogenous octopus G-protein in the dark and this activity is reduced by irradiation with orange light which photoregenerates t-Acid Metarhodopsin back to the initial species, t-rhodopsin.
authors.affiliation: Department of Life Science, Graduate School of Science, Himeji Institute of Technology, Hyogo, Japan.
authors.forename: Akemi
authors.initials: A
authors.lastname: Ashida
authors.forename: Kumi
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Ebrey
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Tsuda
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D015151:Immunoblotting; D049831:Octopodiformes / Q000737:chemistry*; D043562:Receptors, G-Protein-Coupled / Q000302:isolation & purification* / Q000378:metabolism; D012172:Retinaldehyde / Q000378:metabolism; D012243:Rhodopsin / Q000031:analogs & derivatives* / Q000302:isolation & purification* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013053:Spectrophotometry
chemical_list: D043562:Receptors, G-Protein-Coupled; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C013110:metarhodopsins; D012243:Rhodopsin; D012172:Retinaldehyde