Chlamyrhodopsin represents a new type of sensory photoreceptor.
In order to find optimal light conditions for photosynthetic growth, the green alga Chlamydomonas uses a visual system. An optical device, a rhodopsin photoreceptor and an electrical signal transduction chain that mediates between photoreceptor and flagella comprise this system. Here we present an improved strategy for the preparation of eyespot membranes. These membranes contain a retinal binding protein, which has been proposed to be the apoprotein of the phototaxis receptor. The retinal binding protein, which we named chlamyopsin, was purified and opsin-specific antibodies were raised. Using these antibodies, the opsin was localized in the eyespot region of whole cells during growth and cell division. The opsin cDNA was purified and sequenced. The sequence reveals that chlamyopsin is not a typical seven helix receptor. It shows some homology to invertebrate opsins but not to opsins from halobacteria. It contains many polar and charged residues and might function as a light-gated ion channel complex. It is likely that this lower plant rhodopsin diverged from animal opsins early in opsin evolution.
Deininger
W
W
Institut für Biochemie I, Universität Regensburg, Germany.
Kröger
P
P
Hegemann
U
U
Lottspeich
F
F
Hegemann
P
P
D020418:Algal Proteins; D000595:Amino Acid Sequence; D000818:Animals; D001059:Apoproteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D001483:Base Sequence; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D002696:Chlamydomonas / Q000737:chemistry* / Q000254:growth & development; D002846:Chromatography, Affinity; D018076:DNA, Complementary / Q000235:genetics; D005455:Fluorescent Antibody Technique; D047908:Intracellular Signaling Peptides and Proteins; D007473:Ion Channels / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000302:isolation & purification; D008969:Molecular Sequence Data; D010786:Photoreceptor Cells / Q000737:chemistry; D017433:Protein Structure, Secondary; D012172:Retinaldehyde / Q000032:analysis; D012243:Rhodopsin / Q000737:chemistry; D017299:Rod Opsins / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
C020932:11-cis-retinal-binding protein; D020418:Algal Proteins; D001059:Apoproteins; D002352:Carrier Proteins; D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D017299:Rod Opsins; C097338:chlamyopsin protein, Chlamydomonas reinhardtii; D012243:Rhodopsin; D012172:Retinaldehyde