These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Interactions between photoexcited rhodopsin and GTP-binding protein: kinetic and stoichiometric analyses from light-scattering changes.
    Author: Kühn H, Bennett N, Michel-Villaz M, Chabre M.
    Journal: Proc Natl Acad Sci U S A; 1981 Nov; 78(11):6873-7. PubMed ID: 6273893.
    Abstract:
    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.
    [Abstract] [Full Text] [Related] [New Search]