Article date: 1989/3/1
PubMed ID: 2563757
Journal name: Journal of neurochemistry (ISSN: 0022-3042)
The binding of L-[3H]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-[3H]glutamate. The preparation showed high specific binding of L-glutamate with a KD of 0.12 microM and Bmax of 4.7 pmol/mg protein measured in Tris/HCl pH 7.3 and at 4 degrees C. Nonspecific binding was 5-10% of total binding. The glutamate binding was highly stereospecific [K0.5 (D-glutamate), 270 microM] and showed a high degree of discrimination between L-glutamate and L-aspartate [K0.5 (L-aspartate), 54 microM]. In mammalian CNS preparations potent agonists of L-glutamate such as kainate and N-methyl-D-aspartate had no effect at 1 mM, and quisqualate was a weak inhibitor of L-glutamate binding [K0.5 (quisqualate), 162 microM]. Ibotenate was the most potent inhibitor [K0.5 (ibotenate), 0.27 microM], and various esters of L-glutamate were of intermediate potency as displacers of L-[3H]glutamate binding (K0.5 values from 6 to 60 microM). 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.
Author List: Syvertsen C, Fonnum F
Publication Types: Comparative Study; Journal Article
Substances mentioned in the article: Glutamates; Oxadiazoles; Receptors, Glutamate; Receptors, Neurotransmitter; Ibotenic Acid; Aspartic Acid; Glutamic Acid; N-Methylaspartate; Quisqualic Acid; Kainic Acid; Calcium;
Mesh terms: Animals; Aspartic Acid/analogs & derivatives; Astacoidea/metabolism; Binding, Competitive; Calcium/pharmacology; Cell Membrane/metabolism; Glutamates/metabolism; Glutamic Acid; Ibotenic Acid/pharmacology; Kainic Acid/pharmacology; Muscles/metabolism; N-Methylaspartate; Oxadiazoles/pharmacology; Quisqualic Acid; Receptors, Glutamate; Receptors, Neurotransmitter/drug effects; Stereoisomerism;