Biochemical aspects of the visual process
| Autor: | P.A.A. Jansen, S.L. Bonting, Frans J.M. Daemen |
|---|---|
| Rok vydání: | 1970 |
| Předmět: |
Aldimine
genetic structures Lysine Phospholipid Biophysics Protonation Photochemistry Rod Outer Segments Biochemistry Medicinal chemistry Palmitic acid Sodium borohydride chemistry.chemical_compound Endocrinology Dry weight Organic chemistry Molecular Biology Equilibrium constant Phosphatidylethanolamine chemistry.chemical_classification Chromatography Aqueous solution biology Chemistry Chromophore Hexane Enzyme Rhodopsin Docosahexaenoic acid Stability constants of complexes Retinaldehyde biology.protein lipids (amino acids peptides and proteins) Amine gas treating Methanol Stearic acid sense organs Ethylamine Quantitative analysis (chemistry) |
| Zdroj: | Archives of Biochemistry and Biophysics. 140:267-274 |
| ISSN: | 0003-9861 |
| DOI: | 10.1016/0003-9861(70)90031-7 |
| Popis: | In view of diverging opinions on the binding site of 11-cis retinaldehyde in the visual pigment rhodopsin, the effects of neutral and acidic methanol and borohydride-methanol on cattle rhodopsin and on synthetic retinylidene imines were compared with the following results. 1. 1. Extraction of rhodopsin with neutral methanol yielded 70–90% of the chromophore as retinylidene phosphatidylethanolamine. However, addition of phosphatidylethanolamine to a solution of a N-ϵ-retinylidene lysine derivative in neutral methanol resulted in substantial transiminization to retinylidene phosphatidylethanolamine. 2. 2. Acidification of the methanol reduced the amount of retinylidene phosphatidylethanolamine extracted from rhodopsin to virtually zero at 10−2 m HCl. This phenomenon was neither caused by insolubility of the aldimine, nor was it paralleled by a decrease of lipid-soluble phosphorus extractable into the acidified methanol. In a model system consisting of a N-ϵ-retinylidene lysine derivative and a 25-fold molar excess of phosphatidylethanolamine in methanol, transiminization was observed at HCl concentrations of 5.10−4 m or less, but not at 10−3 m HCl or higher. 3. 3. Addition of sodium borohydride to rhodopsin, followed by methanol, gave no indication at all for retinyl phosphatidylethanolamine, whereas retinylidene phosphatidylethanolamine was quantitatively reduced under the same conditions, even in the presence of excess of another free amine. Upon alkaline hydrolysis of the methanol-insoluble residue, left after reduction, the chromophore was located as a compound absorbing around 330 nm, which was tentatively identified as retinyl lysine. The experiments with rhodopsin, interpreted in the light of the model experiments, virtually exclude the possibility that 11-cis retinylidene phosphatidylethanolamine could be the chromophore in native rhodopsin. |
| Databáze: | OpenAIRE |
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