Premium
L‐[ 3 H]Glutamate Binding to a Membrane Preparation from Crayfish Muscle
Author(s) -
Syvertsen Christian,
Fonnum Frode
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.tb02519.x
Subject(s) - glutamate receptor , kainate receptor , biology , biochemistry , binding site , nmda receptor , biophysics , receptor , ampa receptor , microbiology and biotechnology
The binding of L‐[ 3 H]glutamate to an isolated membrane preparation from crayfish tail muscle has been studied. The muscle homogenate was osmotically shocked, frozen and thawed, and thoroughly washed before incubation with L‐[ 3 H]glutamate. The preparation showed high specific binding of L‐glutamate with a K D of 0.12 μ M and B max of 4.7 pmol/mg protein measured in Tris/HCl pH 7.3 and at 4°C. Nonspecific binding was 5–10% of total binding. The gluta‐mate binding was highly stereospecific [ K 0.5 (D‐glutamate), 270 μ M ] and showed a high degree of discrimination between l ‐glutamate and l ‐aspartate [ K 0.5 (L‐aspartate), 54 μ M ]. In mammalian CNS preparations potent agonists of l ‐glutamate such as kainate and N ‐methyl‐ d ‐aspartate had no effect at 1 m M , and quisqualate was a weak inhibitor of l ‐glutamate binding [ K 0.5 (quisqualate), 162 μ M ]. Ibotenate was the most potent inhibitor [ K 0.5 (ibotenate), 0.27 μ M ], and various esters of l ‐glutamate were of intermediate potency as displacers of l ‐[ 3 H]glutamate binding ( K 0.5 values from 6 to 60 μ M ) The glutamate binding site from crayfish muscle is clearly different from any of the subclasses of glutamate receptors in mammalian CNS. A possible physiological function of the binding site is a postsynaptic receptor for glutamate, either an extra‐junctional or a junctional receptor.