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Effect of Halide Ions on t ‐[ 35 S]Butylbicyclophosphorothionate Binding
Author(s) -
Garrett Ken M.,
Blume Arthur J.,
Abel Marc S.
Publication year - 1989
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1989.tb11795.x
Subject(s) - ion , chemistry , binding site , halide , dissociation (chemistry) , saturation (graph theory) , biophysics , inorganic chemistry , biochemistry , biology , mathematics , organic chemistry , combinatorics
The binding of t ‐[ 35 S]butylbicyclophosphoro‐thionate ([ 35 S]TBPS) to a site on the GABA A receptor complex is ion dependent. This study was conducted to determine the effects of ion species and concentration on the time course, affinity, and number of sites of [ 35 S]TBPS binding. At a concentration of 200 m M ion, the time to equilibrium for [ 35 S]TBPS binding was shortest for I ‐ , followed by Br ‐ < CI ‐ < F ‐ . A similar rank order was observed for the concentration of ion required to produce half‐maximal [ 35 S]TBPS binding. Saturation binding experiments were conducted to evaluate the effect of increasing ion concentration on the K D and B max of [ 35 S]TBPS binding. The B max was independent of both ion species and concentration. The receptor affinity, however, increased with increasing concentration for each ion. Calculated maximal affinity values were not different between ions; however, the EC 50 to produce those values was different among ions and ranked in the same order as that for time course and maximal binding data. Association and dissociation rates for [ 35 S]TBPS binding were greater in I ‐ than in Cl ‐ . These data emphasize the importance of ion selection and incubation times on [ 35 S]TBPS binding.