Interactions between photoexcited rhodopsin and GTP-binding protein: kinetic and stoichiometric analyses from light-scattering changes.

In rod outer segments, photoexcited rhodopsin (R*) activates a cyclic GMP phosphodiesterase through a sequence of reactions involving a GTP-binding protein. By measuring light-scattering changes above 700 nm, we have studied the kinetics and stoichiometry of the association of R* with this protein a...

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Prif Awduron: Kühn, H, Bennett, N, Michel-Villaz, M, Chabre, M
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Cyhoeddwyd: 1981
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Research Article
Mynediad Ar-lein:https://ncbi.nlm.nih.gov/pmc/articles/PMC349154/
https://ncbi.nlm.nih.gov/pubmed/6273893
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spelling pubmed-3491542004-03-13 Interactions between photoexcited rhodopsin and GTP-binding protein: kinetic and stoichiometric analyses from light-scattering changes. Kühn, H Bennett, N Michel-Villaz, M Chabre, M Proc Natl Acad Sci U S A Research Article In rod outer segments, photoexcited rhodopsin (R*) activates a cyclic GMP phosphodiesterase through a sequence of reactions involving a GTP-binding protein. By measuring light-scattering changes above 700 nm, we have studied the kinetics and stoichiometry of the association of R* with this protein and of the dissociation of the complex upon GDP/GTP exchange. Two light-scattering signals were obtained upon photoexcitation of rhodopsin in bovine rod outer segment membranes as well as in a reconstituted system consisting of purified GTP-binding protein and washed disc membranes; both signals depended specifically on the presence of GTP-binding protein. A "binding signal" that was observed in the absence of gTP as an increase in turbidity became saturated when a number of rhodopsin molecules equal to the number of GTP-binding protein molecules present (congruent to 10% in rod outer segments) has been bleached, suggesting that the protein binds to R* in a 1:1 complex. A "dissociation signal" of opposite sign, observed in presence of GTP at greater than or equal to 1 microM, is half maximal at 0.04% bleaching and saturated at 0.5% bleaching; it is interpreted as reflecting the dissociation of GTP-binding protein-R* complexes after GDP/GTP exchange on the GTP-binding protein, one R* being able to interact sequentially with about 100 GTP-binding protein molecules. The early time course of the binding signal is faster than that of the dissociation signal, and both signals take place in the 100-msec range at 20 degrees C. 1981-11 /pmc/articles/PMC349154/ /pubmed/6273893 Text en
institution US National Library of Medicine
collection PubMed Central
language en
format Article
topic Research Article
spellingShingle Research Article
Kühn, H
Bennett, N
Michel-Villaz, M
Chabre, M
Interactions between photoexcited rhodopsin and GTP-binding protein: kinetic and stoichiometric analyses from light-scattering changes.
description In rod outer segments, photoexcited rhodopsin (R*) activates a cyclic GMP phosphodiesterase through a sequence of reactions involving a GTP-binding protein. By measuring light-scattering changes above 700 nm, we have studied the kinetics and stoichiometry of the association of R* with this protein and of the dissociation of the complex upon GDP/GTP exchange. Two light-scattering signals were obtained upon photoexcitation of rhodopsin in bovine rod outer segment membranes as well as in a reconstituted system consisting of purified GTP-binding protein and washed disc membranes; both signals depended specifically on the presence of GTP-binding protein. A "binding signal" that was observed in the absence of gTP as an increase in turbidity became saturated when a number of rhodopsin molecules equal to the number of GTP-binding protein molecules present (congruent to 10% in rod outer segments) has been bleached, suggesting that the protein binds to R* in a 1:1 complex. A "dissociation signal" of opposite sign, observed in presence of GTP at greater than or equal to 1 microM, is half maximal at 0.04% bleaching and saturated at 0.5% bleaching; it is interpreted as reflecting the dissociation of GTP-binding protein-R* complexes after GDP/GTP exchange on the GTP-binding protein, one R* being able to interact sequentially with about 100 GTP-binding protein molecules. The early time course of the binding signal is faster than that of the dissociation signal, and both signals take place in the 100-msec range at 20 degrees C.
author Kühn, H
Bennett, N
Michel-Villaz, M
Chabre, M
author_facet Kühn, H
Bennett, N
Michel-Villaz, M
Chabre, M
author_sort Kühn, H
title Interactions between photoexcited rhodopsin and GTP-binding protein: kinetic and stoichiometric analyses from light-scattering changes.
title_short Interactions between photoexcited rhodopsin and GTP-binding protein: kinetic and stoichiometric analyses from light-scattering changes.
title_full Interactions between photoexcited rhodopsin and GTP-binding protein: kinetic and stoichiometric analyses from light-scattering changes.
title_fullStr Interactions between photoexcited rhodopsin and GTP-binding protein: kinetic and stoichiometric analyses from light-scattering changes.
title_full_unstemmed Interactions between photoexcited rhodopsin and GTP-binding protein: kinetic and stoichiometric analyses from light-scattering changes.
title_sort interactions between photoexcited rhodopsin and gtp-binding protein: kinetic and stoichiometric analyses from light-scattering changes.
publishDate 1981
url https://ncbi.nlm.nih.gov/pmc/articles/PMC349154/
https://ncbi.nlm.nih.gov/pubmed/6273893
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