期刊
NEURON
卷 46, 期 6, 页码 879-890出版社
CELL PRESS
DOI: 10.1016/j.neuron.2005.05.009
关键词
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资金
- NEI NIH HHS [R01 EY006837, EY 13748, R01 EY006837-18, R01 EY014596, R01 EY014596-03, R01 EY004939, R37 EY006837-15S1, R01 EY014596-01, R01 EY006837-17, EY 04939, R01 EY014596-02, R37 EY006837, R01 EY006837-16A1, R01 EY001157, R01 EY013748, R37 EY006837-15, EY 01157, NIH EY 06837, F32 EY006837] Funding Source: Medline
- NIDCD NIH HHS [R01 DC006904-01, R01 DC006904] Funding Source: Medline
Retinal rod and cone pigments consist of an apoprotein, opsin, covalently linked to a chromophore, 11-cis retinal. Here we demonstrate that the formation of the covalent bond between opsin and 11-cis retinal is reversible in darkness in amphibian red cones, but essentially irreversible in red rods. This dissociation, apparently a general property of cone pigments, results in a surprisingly large amount of free opsin-about 10% of total opsin-in dark-adapted red cones. We attribute this significant level of free opsin to the low concentration of intracellular free 11-cis retinal, estimated to be only a tiny fraction (similar to 0.1 %) of the pigment content in red cones. With its constitutive transducin-stimulating activity, the free cone opsin produces an similar to 2-fold desensitization in red cones, equivalent to that produced by a steady light causing 500 photoisomerizations s(-1). Cone pigment dissociation therefore contributes to the sensitivity difference between rods and cones.
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