title: Interaction of Asn105 with the retinal chromophore during photoisomerization of pharaonis phoborhodopsin.
abstract: pharaonis phoborhodopsin (ppR; also called pharaonis sensory rhodopsin II, psR-II) is a photoreceptor for negative phototaxis in Natronobacterium pharaonis. ppR has a blue-shifted absorption spectrum with a spectral shoulder, which is highly unique for the archaeal rhodopsin family. The primary reaction of ppR is a cis-trans photoisomerization of the retinal chromophore to form the K intermediate, like the well-studied proton pump bacteriorhodopsin (BR). Recent comparative FTIR spectroscopy of the K states in ppR and BR revealed that more extended structural changes take place in ppR than in BR with respect to chromophore distortion and protein structural changes [Kandori, H., Shimono, K., Sudo, Y., Iwamoto, M., Shichida, Y., and Kamo, N. (2001) Biochemistry 40, 9238-9246]. FTIR spectroscopy of the N105D mutant protein reported here assigns the vibrational bands at 1704 and 1700 cm(-1) as C=O stretches of Asn105 in ppR and ppR(K), respectively. A comparative investigation between ppR and BR further reveals that the structure at position 105 in ppR is similar to that of the corresponding position (Asp115) in BR; this observation is supported by the recent X-ray crystallographic structures of ppR [Luecke, H., Schobert, B., Lanyi, J. K., Spudich, E. N., and Spudich, J. L. (2001) Science 293, 1499-1503; Royant, A., Nollert, P., Edman, K., Neutze, R., Landau, E. M., Pebay-Peyroulla, E., and Navarro, J. (2001) Proc. Natl. Acad. Sci. U.S.A. 98, 10131-10136]. Nevertheless, structural changes upon photoisomerization at position 105 in ppR are greater than those at position 115 in BR. As a consequence of a unique chromophore-protein interaction in ppR, extended protein structural changes accompanying retinal photoisomerization occur, and these include Asn105 which is approximately 7 A from the retinal chromophore.
authors.affiliation: Department of Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan. kandori@ach.nitech.ac.jp
authors.forename: Hideki
authors.initials: H
authors.lastname: Kandori
authors.forename: Kazumi
authors.initials: K
authors.lastname: Shimono
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Shichida
authors.forename: Naoki
authors.initials: N
authors.lastname: Kamo
mesh_terms: D019943:Amino Acid Substitution; D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism; D001216:Asparagine; D001665:Binding Sites; D002338:Carotenoids / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D019617:Halobacterium salinarum / Q000378:metabolism; D025602:Halorhodopsins; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012172:Retinaldehyde / Q000378:metabolism*; D025603:Sensory Rhodopsins; D013055:Spectrophotometry, Infrared
chemical_list: D019843:Archaeal Proteins; D025602:Halorhodopsins; D011994:Recombinant Proteins; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal; D002338:Carotenoids; D001216:Asparagine; D012172:Retinaldehyde