[Molecular mechanisms of receptor-potential generation by the photoreceptor. III. Conformational transition responsible for the tail end of the photoresponse of an artificial lipid membrane modified by fragments of the external segments of rods].
The kinetics of photoinduced changes of protein fluorescence of cattle visual pigment was studied in the presence of hydroxylamine. The rate constant of fluorescence increase is proportional to NH2OH concentration when it is less than 0.4 M. It reaches the maximal magnitude (3.3 +/- 1 sec-1) at higher hydroxylamine concentration. Fluorescence increase rate is controlled by the rate of chemical reaction of rhodopsin with hydroxylamine. It is limited by conformational rearrangement of opsin. This rearrangement does not induce absorbance spectrum change of visual pigment, but confers to it the capability to react with NH2OH and NaBH4. Kinetic parameters of this rearrangement (tau 20 degrees C approximately 300 msec, Eact = 19 +/- 2 kcal/mole) coincide with kinetic parameters of diminishing of the photoresponse of artificial lipid membrane modified by fragments of rod outer segments in the temperature range studied (+2 divided by +25 degrees C).
D000818:Animals; D002417:Cattle; D005453:Fluorescence; D006898:Hydroxylamines; D008027:Light; D008563:Membrane Lipids / Q000528:radiation effects; D008567:Membranes, Artificial; D010786:Photoreceptor Cells / Q000502:physiology* / Q000528:radiation effects* / Q000648:ultrastructure; D011487:Protein Conformation / Q000528:radiation effects; D012168:Retinal Pigments / Q000528:radiation effects*; D012243:Rhodopsin / Q000528:radiation effects*; D013696:Temperature
D006898:Hydroxylamines; D008563:Membrane Lipids; D008567:Membranes, Artificial; D012168:Retinal Pigments; D012243:Rhodopsin
Molekuliarnye mekhanizmy generatsii retseptornogo potentsiala fotoretseptorom. III. Izuchenie konformatsionnogo perekhoda otvetstvennogo za zadniĭ front fotootveta iskusstvennoĭ lipidnoĭ membrany, modifitsirovannoĭ fragmentami naruzhnogo segmenta palochki.