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SHAPE OF THE CHROMOPHOIW BINDING SITE IN pharaonis PHOBORHODOPSIN FROM A STUDY USING RETINAL ANALOGS
Author(s) -
Hirayama Junichi,
Imamoto Yasushi,
Shichida Yoshinori,
Yoshizawa Tǒru,
Asato Alfred E.,
Liu Robert S. H.,
Kamo Naoki
Publication year - 1994
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1994.tb05121.x
Subject(s) - retinal , chromophore , retinaldehyde , opsin , bacteriorhodopsin , chemistry , stereochemistry , isopropyl , ring (chemistry) , halobacteriaceae , binding site , rhodopsin , photochemistry , biochemistry , organic chemistry , halobacterium salinarum , membrane
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, α‐retinal, cyclohexylretinal and 5‐isopropyl‐α‐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.