Enhancement of opsin activity by all-trans-retinal.
The rod cell photoreceptor apoprotein, opsin, activates the G-protein, transducin, although at a much reduced level than light-activated rhodopsin. The ability of all-trans-retinal to enhance opsin apoprotein activity was investigated using a guanyl nucleotide exchange assay on transducin. All-trans-retinal enhanced opsin activity in a concentration-dependent manner. At high concentrations of all-trans-retinal, the activity of the all-trans-retinal-opsin complex was comparable to that from an equimolar amount of metarhodopsin(II). However, in contrast to metarhodopsin(II), the active all-trans-retinalopsin complex did not require a stable Schiff base linkage between opsin and all-trans-retinal. The lack of a stable Schiff base and differences in activity at high pH imply that opsin and all-trans-retinal form a complex that is distinct from metarhodopsin(II). The ability of all-trans-retinal to stimulate the transduction cascade may be a source of post-bleach noise in photoreceptors.
Surya
A
A
Department of Biochemistry and Molecular Biology, SUNY Health Science Center at Syracuse 13210, USA.
Knox
B E
BE
D000818:Animals; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D011489:Protein Denaturation; D012172:Retinaldehyde / Q000494:pharmacology*; D012243:Rhodopsin / Q000031:analogs & derivatives / Q000378:metabolism; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D017299:Rod Opsins / Q000378:metabolism*; D012545:Schiff Bases / Q000378:metabolism; D015293:Transducin / Q000378:metabolism; D014785:Vision, Ocular
D017299:Rod Opsins; D012545:Schiff Bases; C013110:metarhodopsins; D012243:Rhodopsin; D015293:Transducin; D012172:Retinaldehyde