The glutamate receptor-like protein of brain synaptic membranes is a metalloprotein.

The glutamate binding glycoprotein from rat brain synaptic plasma membranes was found to be quite sensitive to inhibition by sodium azide (NaN₃. The glutamate binding activity of the purified glycoprotein was decreased to 50% in the presence of 0.33 mM NaN₃. Similar concentrations of NaN₃ also caused 50% inhibition of glutamate binding to the synaptic membranes. Analysis of the purified binding protein for its content of iron and sulfur revealed the presence of 1.95 g atom Fe and 2.19 g atom S per mole of 14,000 M.W. protein. On the basis of changes in the difference spectra of this protein it is believed that both the azide effect and the glutamate binding are taking place at a site which contains the Fe₂S₂ center.