Activity of rhodopsin in vitamin A-deprived rats: light-dependent binding of G-protein.
Levels of rhodopsin in the photoreceptors of Long-Evans rats were reduced by approximately 55% through dietary deprivation of vitamin A. The interaction of visual pigment with G-protein was examined in receptor outer segment (ROS) membranes obtained from these animals. A binding assay was used to quantitate affinity of the visual pigment in unbleached and bleached ROS membranes for the alpha and beta subunits of exogenous G-protein. Extents of binding were similar to those observed for ROS membranes of rats raised on a normal (vitamin A-supplemented) diet. The results are consistent with a normal capacity for G-activation by photoactivated rhodopsin (R*) in vitamin A-deprived animals. They further indicate that "free opsin" arising in vitamin A deficiency, unlike R*, has relatively low affinity for G-protein.
Pepperberg
D R
DR
Department of Ophthalmology, University of Illinois College of Medicine, Chicago 60612.
Anderson
S M
SM
Crouch
R
R
D000818:Animals; D004586:Electrophoresis; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins; D008027:Light; D010507:Periodicity; D051381:Rats; D012168:Retinal Pigments / Q000378:metabolism*; D012243:Rhodopsin / Q000378:metabolism*; D014802:Vitamin A Deficiency / Q000378:metabolism*
C488950:Gnat1 protein, rat; D012168:Retinal Pigments; D012243:Rhodopsin; D019204:GTP-Binding Proteins; D020962:Heterotrimeric GTP-Binding Proteins