Light-dependent phosphorylation of rhodopsin: number of phosphorylation sites

The light-dependent phosphorylation of bovine and frog rhodopsin was investigated under various conditions with suspensions of isolated rod outer segments. For both bovine rhodopsin and frog rhodopsin the average phosphorylation extent was found to be as high as 7.0 plus or minus 0.3 mol of phosphat...

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Bibliographic Details
Published in:Biochemistry (Easton) 1982-06, Vol.21 (12), p.3014-3022
Main Authors: Wilden, Ursula, Kuehn, Hermann
Format: Article
Language:English
Subjects:
Animals
Binding Sites
Cattle
Darkness
eye
frogs
In Vitro Techniques
Light
Phosphates - metabolism
Phosphorylation
Photochemistry
Rana esculenta
Retinal Pigments - metabolism
rhodopsin
Rhodopsin - isolation & purification
Rhodopsin - metabolism
Rod Cell Outer Segment - metabolism
rod outer segment membranes
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Summary:The light-dependent phosphorylation of bovine and frog rhodopsin was investigated under various conditions with suspensions of isolated rod outer segments. For both bovine rhodopsin and frog rhodopsin the average phosphorylation extent was found to be as high as 7.0 plus or minus 0.3 mol of phosphate/mol of rhodopsin (7 P/R) under optimal incubation conditions. Phosphate incorporation in the dark was 50-100 times lower. Phosphorylated bovine rhodopsin was separated into rhodopsin fractions of different phosphorylation extents by means of ion-exchange chromatography, in order to get information about the distribution of individual phosphorylation extents on different rhodopsin molecules in a population of known average phosphorylation extent. The distribution was always found to be rather inhomogeneous. The highest individual phosphorylation extent found was 9 P/R; all intermediate phosphorylation extents between 0 and 9 P/R were also found. This experiment suggests that there is some but not a strong cooperativity between the individual phosphorylation sites.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00541a032