title: Shape of the chromophore binding site in pharaonis phoborhodopsin from a study using retinal analogs.
abstract: To investigate the shape of the chromophore binding site of pharaonis phoborhodopsin (ppR), ppR-opsin was incubated with five ring-modified retinal analogs: an acyclic retinal, phenylretinal, alpha-retinal, cyclohexylretinal and 5-isopropyl-alpha-retinal. The experimental results were compared with those obtained from bacteriorhodopsin-opsin (bR-opsin) and the same retinal analogs. It was suggested that ring chain conformation is important in affecting the spectral shoulder unique for the absorption spectrum of ppR. The rate of pigment formation depended greatly on the analogs used with the planar analogs showing rapid formation. Thus, we concluded that the space of the retinal binding site of ppR is restricted to the plane of the cyclohexenyl ring of the chromophore, whereas that of bR is less restricted.
authors.affiliation: Department of Biophysical Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Hirayama
authors.forename: Y
authors.initials: Y
authors.lastname: Imamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Shichida
authors.forename: T
authors.initials: T
authors.lastname: Yoshizawa
authors.forename: A E
authors.initials: AE
authors.lastname: Asato
authors.forename: R S
authors.initials: RS
authors.lastname: Liu
authors.forename: N
authors.initials: N
authors.lastname: Kamo
mesh_terms: D019843:Archaeal Proteins; D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D001665:Binding Sites; D002338:Carotenoids; D006216:Halobacteriaceae / Q000378:metabolism*; D025602:Halorhodopsins; D012172:Retinaldehyde / Q000031:analogs & derivatives* / Q000378:metabolism*; D025603:Sensory Rhodopsins; D013053:Spectrophotometry; D013329:Structure-Activity Relationship
chemical_list: D019843:Archaeal Proteins; D025602:Halorhodopsins; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal; D002338:Carotenoids; D001436:Bacteriorhodopsins; D012172:Retinaldehyde