Reduced Light-dependent Phosphorylation of an Analog Visual Pigment Containing 9-Demethylretinal as Its Chromophore

9-Demethyl rhodopsin (9dR), an analog of vertebrate rhodopsin, consists of opsin and a covalently attached chromophore of 11- cis 9-demethylretinal. Electrophysiological evidence that photoactivated 9dR (9dR*) undergoes abnormally slow deactivation in salamander rods (Corson, D. W., Cornwall, M. C.,...

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Bibliographic Details
Published in:The Journal of biological chemistry 1995-03, Vol.270 (12), p.6718-6721
Main Authors: Morrison, D F, Ting, T D, Vallury, V, Ho, Y K, Crouch, R K, Corson, D W, Mangini, N J, Pepperberg, D R
Format: Article
Language:English
Subjects:
Animals
Cattle
Light
Phosphorylation
Retinaldehyde - metabolism
Rhodopsin - analogs & derivatives
Rhodopsin - metabolism
Rod Cell Outer Segment - metabolism
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Summary:9-Demethyl rhodopsin (9dR), an analog of vertebrate rhodopsin, consists of opsin and a covalently attached chromophore of 11- cis 9-demethylretinal. Electrophysiological evidence that photoactivated 9dR (9dR*) undergoes abnormally slow deactivation in salamander rods (Corson, D. W., Cornwall, M. C., and Pepperberg, D. R.(1994) Visual Neurosci. 11, 91-98) raises the possibility that opsin phosphorylation, a reaction involved in visual pigment deactivation, operates abnormally on 9dR*. This possibility was tested by measuring the light-dependent phosphorylation of 9dR in preparations obtained from bovine rod outer segments. Outer segment membranes containing 9dR or regenerated rhodopsin were flash-illuminated in the presence of [ - P]ATP and rhodopsin kinase, further incubated in darkness, and then analyzed for opsin-bound [ P]P i . [ P]P i incorporation by 9dR* increased with both incubation period and bleaching extent but, under all conditions tested, was less than that measured in rhodopsin controls. Results obtained with 30-s incubation periods indicated that the maximal initial rate of incorporation by 9dR* is about 25% of that by photoactivated rhodopsin. The results imply that the low incorporation of P i by 9dR* results from a reduced rate of phosphorylation by rhodopsin kinase and are consistent with the prolonged lifetime of 9dR* determined electrophysiologically.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.270.12.6718