Immunochemical and immunohistochemical characterization of a synaptic membrane protein that binds the competitive antagonists of NMDA receptors

An ~ 54-kDa protein that has binding sites for the competitive N- methyl- d-aspartate (NMDA) receptor antagonists 3-((±)-2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid (CPP) and (±)-(E)-2-amino-4-propyl-5-phosphonopentenoic acid (CGP 39653) was purified from rat brain synaptic membranes. Polyclonal antibodies to this protein reacted specifically with an ~ 54-kDa protein in synaptic membranes and immunoextracted ~ 60% of [ 3H]CGP 39653 binding sites associated with solubilized membrane proteins. The antibodies also labeled antigenic sites in the perikaryon and apical and basilar dendrites of pyramidal neurons of the hippocampus and cerebral cortex.