title: The role of retinal light induced dipole in halorhodopsin structural alteration.
abstract: The present work studies the mechanism of light induced protein conformational changes in the over-expressed mutant of halorhodopsin (phR) from Natronomonas pharaonis. The catalytic effect of light is reflected in accelerating hydroxyl amine reaction rate of light adapted phR. Light catalysis was detected in native phR but also in artificial pigments derived from tailored retinal analogs locked at the crucial C13=C14 double bond. It is proposed that the photoexcited retinal chromophore induces protein concerted motion that decreases the energy gap between reactants ground and transition states. This energy gap is overcome by coupling to specific protein vibrations. Surprisingly, the rate constants show unusual decreasing trend following temperature increase both for native and artificial pigments.
authors.affiliation: Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Sansa
authors.initials: S
authors.lastname: Dutta
authors.affiliation: Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Amiram
authors.initials: A
authors.lastname: Hirshfeld
authors.affiliation: Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel. Electronic address: mudi.sheves@weizmann.ac.il.
authors.forename: Mordechai
authors.initials: M
authors.lastname: Sheves
mesh_terms: D000588:Amines / Q000737:chemistry / Q000378:metabolism; D055162:Biocatalysis; D003624:Darkness; D006216:Halobacteriaceae; D025602:Halorhodopsins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007536:Isomerism; D008027:Light; D009154:Mutation; D011487:Protein Conformation / Q000528:radiation effects; D012172:Retinaldehyde / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000588:Amines; D025602:Halorhodopsins; D012172:Retinaldehyde
keywords: Halorhodopsin; Isomerization; Light induced dipole; Rhodopsin