title: Archaeal-type rhodopsins in Chlamydomonas: model structure and intracellular localization.
abstract: Phototaxis in the unicellular green alga Chlamydomonas reinhardtii is mediated by rhodopsin-type photoreceptor(s). Recent expressed sequence tag database from the Kazusa DNA Research Institute has provided the basis for unequivocal identification of two archaeal-type rhodopsins in it. Here we demonstrate that one is located near the eyespot, wherein the photoreceptor(s) has long been thought to be enriched, along with the results of bioinformatic analyses. Secondary structure prediction showed that the second putative transmembrane helices (helix B) of these rhodopsins are rich in glutamate residues, and homology modeling suggested that some additional intra- or intermolecular interactions are necessary for opsin-like folding of the N-terminal ca. 300-aa membrane spanning domains of 712 and 737-aa polypeptides. These results complement physiological and electrophysiological experiments combined with the manipulation of their expression [O.A. Sineshchekov, K.H. Jung, J.H. Spudich, Proc. Natl. Sci. USA 99 (2002) 8689; G. Nagel, D. Olig, M. Fuhrmann, S. Kateriya, A.M. Musti, E. Bamberg, P. Hegemann, Science 296 (2002) 2395].
authors.affiliation: School of Materials Science, Japan Advanced Institute of Science and Technology, Asahidai, Tatsunokuchi, Nomi-gun, Ishikawa, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Kenta
authors.initials: K
authors.lastname: Yamasaki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Fujita
authors.forename: Kazushi
authors.initials: K
authors.lastname: Oda
authors.forename: Mineo
authors.initials: M
authors.lastname: Iseki
authors.forename: Kazuichi
authors.initials: K
authors.lastname: Yoshida
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Watanabe
authors.forename: Hiromi
authors.initials: H
authors.lastname: Daiyasu
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Toh
authors.forename: Eriko
authors.initials: E
authors.lastname: Asamizu
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tabata
authors.forename: Kenji
authors.initials: K
authors.lastname: Miura
authors.forename: Hideya
authors.initials: H
authors.lastname: Fukuzawa
authors.forename: Shogo
authors.initials: S
authors.lastname: Nakamura
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Takahashi
mesh_terms: D020418:Algal Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D019843:Archaeal Proteins / Q000235:genetics; D016825:Chlamydomonas reinhardtii / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics; D012243:Rhodopsin / Q000032:analysis* / Q000737:chemistry* / Q000235:genetics; D025604:Rhodopsins, Microbial / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D020418:Algal Proteins; D019843:Archaeal Proteins; D015800:Protozoan Proteins; D025604:Rhodopsins, Microbial; D012243:Rhodopsin