SOLUBILIZATION, CHARACTERIZATION, AND PARTIAL-PURIFICATION OF ALPHA-AMINO-3-HYDROXY-5-METHYL-4-ISOXAZOLEPROPIONIC ACID-SENSITIVE QUISQUALATE-SENSITIVE KAINATE-SENSITIVE L-GLUTAMATE BINDING-SITES FROM PORCINE BRAIN SYNAPTIC JUNCTIONS

L-[H-3]Glutamate binding sites were solubilized from porcine brain synaptic junctions by Triton X-114 in the presence of KCl. The solubilized binding sites bound L-[H-3]glutamate reversibly with K(D) and B(max) values of 1.48 +/- 0.18-mu-M and 178.2 +/- 15.9 pmol/mg of protein, respectively. These binding sites appeared to be integral membrane glycoproteins, with sugar moieties recognized by wheat germ agglutinin. A 49.3-fold purification of these binding sites was achieved by Triton X-114 solubilization, anion-exchange chromatography, and affinity chromatography using wheat germ agglutinin-Sepharose. The apparent molecular mass of the partially purified binding sites was 620 +/- 50 kDa. L-[H-3]Glutamate bound to the solubilized preparation could be effectively displaced by agonists of non-N-methyl-D-aspartate (NMDA) L-glutamate receptors but not by NMDA or alpha-amino-4-phosphonobutyrate. The rank order for the competitive ligands in displacing L-[H-3]glutamate was: quisqualate > alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid > L-glutamate > kainate.