Light-dependent changes in G-protein binding to ROS membranes in intact Bufo retinas

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Publication Type Journal Article
School or College School of Medicine
Department Ophthalmology
Creator Baehr, Wolfgang
Other Author Mangini, N J; Pepperberg, D R
Title Light-dependent changes in G-protein binding to ROS membranes in intact Bufo retinas
Date 1986
Description Light-dependent changes in the binding of G-protein were analyzed in outer segment disk membranes obtained from photoreceptors of the toad (Bufo marinus) retina. Isolated, intact retinas, incubated in oxygenated Ringer's solution at 23 +/- 1 degree C, were subjected to various conditions of illumination and then incubated in darkness for specified periods. The retinas were then chilled (0-4 degrees C) and the receptor outer segments (ROS) were isolated. Binding of the alpha- and beta-subunits of G-protein to the ROS membranes was analyzed by quantitating G alpha and G beta extracted from the membranes with hypotonic medium lacking GTP vs. hypotonic medium containing GTP (H and HG extracts, respectively). For retinas illuminated and then immediately chilled for analysis, the extent of G binding (relative abundance of G alpha, beta in the HG extract) increased with the extent of bleaching of the visual pigment. Near-maximal binding was observed after bleaches of greater than or equal to 30%. With an increasing period of incubation in darkness after approximately 70% bleaching, the extent of binding declined gradually to low levels characteristic of unbleached retinas. The period required for half-completion of the decline was approximately 10(3) s. A gradual decline in G binding, from a rapidly developing peak value, was also observed with an increasing period of exposure to intense light. Viewed in the context of previous electrophysiological data, our results indicate that sustained bleaching desensitization of the rods does not depend upon a persisting state of "tight binding" (immobilization) of G-protein by bleached visual pigment.
Type Text
Publisher Rockefeller University Press
Volume 88
Issue 5
First Page 675
Last Page 694
Subject Centrifugation, Density Gradient; Membranes; Adaptation, Physiological
Subject MESH GTP-Binding Proteins; Photoreceptors; Rod Outer Segments
Language eng
Bibliographic Citation Mangini NJ, Pepperberg DR, Baehr W. (1986). Light-dependent changes in G-protein binding to ROS membranes in intact Bufo retinas. J Gen Physiol, 88(5), 675-94
Rights Management (c) Rockefeller University Press
Format Medium application/pdf
Identifier ir-main,1711
ARK ark:/87278/s6v41cb2
Setname ir_uspace
Date Created 2012-06-13
Date Modified 2021-05-06
ID 703232
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