Abstract
The binding site of retinaldehyde during photolysis of rhodopsin was studied by probing the retinaldehyde binding site of native rhodopsin after illumination. This was carried out by NaBH 4 fixation of the chromophore during and at various time intervals after illumination, followed by treatment with 11- cis-retinaldehyde. With NaBH 4 present during illumination there is very little recombination with 11- cis-retinaldehyde. With increasing time intervals between illumination and addition of NaBH 4 the recombination activity increases. This increase follows first order kinetics with a half time of about 10 min at 25 °C. This coincides with the decay of metarhodopsin II at this temperature as confirmed by the time course of the appearance of free retinaldehyde. Thus the recombination capacity of illuminated, reduced rhodopsin parallels the vacation of the metarhodopsin II-binding site. This indicates that in intact rhodopsin and in metarhodopsin II retinaldehyde is bound to the same ϵ-amino lysine group, while migration of the chromophore occurs during the decay of metarhodopsin II.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Bioenergetics
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