Structure and photobleaching process of chicken iodopsin.
Iodopsin, a dominant cone pigment in a chicken retina, has an absorption spectrum in longer wavelength region than rhodopsin. To account for this red-shift of iodopsin, we had proposed a structural model from retinal analogue experiments, in which iodopsin would have a relatively long distance between the protonated Schiff base nitrogen and the counterion. This was confirmed by a resonance Raman spectroscopy. The photochemical properties of iodopsin were studied and compared with those of rhodopsin, which revealed the following differences. The regeneration rate of iodopsin with 11-cis-retinal was 240 times faster than rhodopsin. Meta-iodopsin II, the signalling state of iodopsin, decayed about 100 times faster than meta-rhodopsin II. The Km value of meta-iodopsin II and rhodopsin kinase was lower than meta-rhodopsin II. These results are in consistent with rapid adaptation and low photosensitivity of cones relative to those of rods.
Yoshizawa
T
T
Department of Information Systems Engineering, Faculty of Engineering, Osaka Sangyo University, Japan.
Imamoto
Y
Y
D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D005136:Eye Proteins; D051606:G-Protein-Coupled Receptor Kinase 1; D006801:Humans; D007700:Kinetics; D010777:Photochemistry; D011494:Protein Kinases / Q000378:metabolism; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology; D012168:Retinal Pigments / Q000737:chemistry* / Q000378:metabolism*; D012172:Retinaldehyde / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry; D017299:Rod Opsins; D017386:Sequence Homology, Amino Acid; D013053:Spectrophotometry
D005136:Eye Proteins; D012168:Retinal Pigments; D017299:Rod Opsins; C034941:iodopsin; D012243:Rhodopsin; D011494:Protein Kinases; D051606:G-Protein-Coupled Receptor Kinase 1; C496764:GRK1 protein, human; D012172:Retinaldehyde