title: FTIR spectroscopy of the M photointermediate in pharaonis rhoborhodopsin.
abstract: pharaonis phoborhodopsin (ppR; also called pharaonis sensory rhodopsin II, psR-II) is a photoreceptor for negative phototaxis in Natronobacterium pharaonis. During the photocycle of ppR, the Schiff base of the retinal chromophore is deprotonated upon formation of the M intermediate (ppR(M)). The present FTIR spectroscopy of ppR(M) revealed that the Schiff base proton is transferred to Asp-75, which corresponds to Asp-85 in a light-driven proton-pump bacteriorhodopsin (BR). In addition, the C==O stretching vibrations of Asn-105 were assigned for ppR and ppR(M). The common hydrogen-bonding alterations in Asn-105 of ppR and Asp-115 of BR were found in the process from photoisomerization (K intermediate) to the primary proton transfer (M intermediate). These results implicate similar protein structural changes between ppR and BR. However, BR(M) decays to BR(N) accompanying a proton transfer from Asp-96 to the Schiff base and largely changed protein structure. In the D96N mutant protein of BR that lacks a proton donor to the Schiff base, the N-like protein structure was observed with the deprotonated Schiff base (called M(N)) at alkaline pH. In ppR, such an N-like (M(N)-like) structure was not observed at alkaline pH, suggesting that the protein structure of the M state activates its transducer protein.
authors.affiliation: Department of Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Furutani
authors.forename: Masayuki
authors.initials: M
authors.lastname: Iwamoto
authors.forename: Kazumi
authors.initials: K
authors.lastname: Shimono
authors.forename: Naoki
authors.initials: N
authors.lastname: Kamo
authors.forename: Hideki
authors.initials: H
authors.lastname: Kandori
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects*; D001436:Bacteriorhodopsins / Q000737:chemistry / Q000528:radiation effects; D002338:Carotenoids / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects*; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D025602:Halorhodopsins; D006863:Hydrogen-Ion Concentration; D008027:Light; D008081:Liposomes / Q000737:chemistry; D010777:Photochemistry / Q000379:methods; D011487:Protein Conformation; D017494:Proton Pumps / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D025603:Sensory Rhodopsins; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013329:Structure-Activity Relationship; D013696:Temperature
chemical_list: D019843:Archaeal Proteins; D025602:Halorhodopsins; D008081:Liposomes; D017494:Proton Pumps; D011994:Recombinant Proteins; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal; D002338:Carotenoids; D001436:Bacteriorhodopsins