High-affinity glutamic acid binding to brain synaptic membranes |
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Authors: | Elias K. Michaelis Mary L. Michaelis Louis L. Boyarsky |
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Affiliation: | 1. Neurobiology Section, Department of Human Development, University of Kansas, Lawrence, Kan. 66045 U.S.A.;2. Department of Physiology and Biophysics, University of Kentucky, Lexington, Ky. U.S.A. |
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Abstract: | Rat brain homogenate preparations exhibited two types of glutamine binding, one a high-affinity (K1 = 0.2 μM) and the other a low-affinity type (K2 = 4.4 μM). The high-affinity binding was primarily associated with the plasma membrane subcellular fractions and in particular with the synaptic membrane subfraction. This l-glutamate binding was found to be strongly stereospecific for the l-form and was almost totally reversible. The synaptic membrane glutamate binding was partialy inhibited by neuro-excitatory and neuro-inhibitory amino acids but was not affected by amino acids lacking in neuropharmacologic activity. The membrane-associated l-glutamate binding system could be solubilized by Triton X-100 without loss of its high-affinity binding activity. The chemical nature of this glutamate binding component was found to be that of a glycolipoprotein. It is proposed that this glutamate binding system represents the physiologic receptor on neuronal membranes of this amino acid. |
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