Synthesis of [3H]2-amino-4-phosphonobutyric acid and characterization of its binding to rat brain membranes: a selective ligand for the chloride/calcium-dependent class of L-glutamate binding sites.
[3H]2-amino-4-phosphonobutyric acid was synthesized by the conjugate addition of 1-lithio-2-trimethylsilyethyne to diethyl ethynylphosphate followed by catalytic tritiation and hydrolysis. Radiolabelled 2-amino-4-phosphonobutyric acid binds to a distinct class of L-glutamate binding sites and does not exhibit appreciable binding to sites not displaced by L-glutamate. The binding affinity (Kd = 5.1 +/- 0.4 microM) and pharmacological profile correspond to those values obtained from physiological studies of 2-amino-4-phosphonobutyric acid inhibition of synaptic transmission, and to those values obtained in [3H]L-glutamate binding assays. [3H]2-amino-4-phosphonobutyric acid does not exhibit significant binding to the Cl-/Ca2+-independent L-glutamate binding site(s), nor to the Na+-dependent L-glutamate binding site (up to 50 mM Na+). These data provide further evidence that the physiological action of 2-amino-4-phosphonobutyric acid is mediated by the previously described Cl-/Ca2+-dependent L-glutamate binding sites, and provides an assay system which is optimal for the study of these sites.
D000613:Aminobutyrates / Q000096:biosynthesis* / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000502:physiology*; D005971:Glutamates / Q000378:metabolism* / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D051381:Rats; D011919:Rats, Inbred Strains; D013569:Synapses / Q000378:metabolism; D013696:Temperature; D014316:Tritium
D000613:Aminobutyrates; D002712:Chlorides; D005971:Glutamates; D008024:Ligands; D014316:Tritium; C012729:2-amino-4-phosphonobutyric acid; D002118:Calcium