CHLAMYRHODOPSIN REPRESENTS A NEW-TYPE OF SENSORY PHOTORECEPTOR

In order to find optimal light conditions for photosynthetic growth, t he green alga Chlamydomonas uses a visual system, An optical device, a rhodopsin photoreceptor and an electrical signal transduction chain t hat mediates between photoreceptor and flagella comprise this system, Here we present an improved strategy for the preparation of eyespot me mbranes, These membranes contain a retinal binding protein, which has been proposed to be the apoprotein of the phototaxis receptor, The ret inal binding protein, which we named chlamyopsin, was purified and ops in-specific antibodies were raised, Using these antibodies, the opsin was localized in the eyespot region of whole cells during growth and c ell devision, The opsin cDNA was purified and sequenced, The sequence reveals that chlamyopsin is not a typical seven helix receptor. It sho ws some homology to invertebrate opsins but not to opsins from halobac teria, It contains many polar and charged residues and might function as a light-gated ion channel complex, It is likely that this lower pla nt rhodopsin diverged from animal opsins early in opsin evolution.