High-affinity glutamic acid binding to brain synaptic membranes

High affinity glutamate binding during postnatal development of rat cerebellum

“…The dissociation constant (fed) of specific 'binding' was 0.22 + 0.13 PM. This is in good agreement with the data in [10, 13,14]. However the density of sites (10.1 z!z 2.2 pmol/mg protein) is much lower than the value found in [lo].…”

“…'Specific' binding occurs in a sodium-free medium, it is slightly inhibited by increasing ionic strength of the assay medium (results not shown) and when the assay was performed at 37"C, the 'specific' binding slightly decreased (-10%) (fig2B); the optimal pH is -7.1 (results not shown). The fact that the & found in [10, 13,14] iS lower than any & measured for glUtamate transport at high or even extra-high affinity and the fact that 'specific' binding occurs in sodiumfree medium and at low ionic strength indicate that the sites involved in 'specific' binding are different from those involved in glutamate transport.…”

Distinguishing characteristics between glutamate and kainic acid binding sites in brain synaptic membranes

“…We have shown that brain synaptic membranes are enriched in high affinity L-[3H]glutamic acid binding sites which have a number of the pharmacologic characteristics of the receptor for this excitatory amino acid [5,13,14]. It was also shown that this high affmity glutamate binding activity of synaptic membranes is associated with a small molecular weight glycoprotein [ 151.…”

“…It was also shown that this high affmity glutamate binding activity of synaptic membranes is associated with a small molecular weight glycoprotein [ 151. Glutamate binding to this protein exhibits a similar pattern of sensitivity to various glutamate analogs as does the binding of L-glutamate to the synaptic membranes [5,14,15]. However, the binding of L-[3H]glutamic acid either to the synaptic membranes [6,14] or to the purified binding protein [14] is not affected by the presence of a 103-fold greater concentration of kainic acid.…”

Molecular Characteristics of Membrane Glutamate Receptor-Ionophore Interaction

“…The synaptic plasma membrane fraction obtained following osmotic rupture of these nerve endings has been found to be enriched in glutamate binding activity which has many of the expected characteristics of the excitatory amino acid receptors (Michaelis, et al, 1974). …”