Archaeal-type rhodopsins in Chlamydomonas: model structure and intracellular localization.
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].
Suzuki
Takeshi
T
School of Materials Science, Japan Advanced Institute of Science and Technology, Asahidai, Tatsunokuchi, Nomi-gun, Ishikawa, Japan.
Yamasaki
Kenta
K
Fujita
Satoshi
S
Oda
Kazushi
K
Iseki
Mineo
M
Yoshida
Kazuichi
K
Watanabe
Masakatsu
M
Daiyasu
Hiromi
H
Toh
Hiroyuki
H
Asamizu
Eriko
E
Tabata
Satoshi
S
Miura
Kenji
K
Fukuzawa
Hideya
H
Nakamura
Shogo
S
Takahashi
Tetsuo
T
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
D020418:Algal Proteins; D019843:Archaeal Proteins; D015800:Protozoan Proteins; D025604:Rhodopsins, Microbial; D012243:Rhodopsin