Association of [14C]glutamate with the protein components of synaptic membrane preparations

Calf brain synaptic plasma membranes were saturated under extracellular conditions with [14C]glutamic acid and the resulting labelled membranes fractionated with 0.9% NaCl, distilled water, n-butanol-water, 0.05 mol/L NaOH and 0.5% Triton X-100 solutions in this order. Triton X-100 was the most effective solubilizer, liberating altogether about 24% of the membrane proteins, but only 4-7% of the label, while NaOH was the most potent solubilizer for the protein-bound label (50-70%). Slab gel electrophoresis showed significant qualitative differences in the banding patterns of the protein extracts, but only two fractions, a low-molecular weight (around 15 kd) and a high-molecular weight (greater than 200 kd) fraction bound [14C]glutamate.