Characterization of a specific L-[3H]glutamic acid binding site on cilia isolated fromParamecium tetraurelia

Cilia isolated fromParamecium tetraurelia possess a specific, high affinity L-[3H]glutamic acid binding site, defined by an ED50 of 3.0×10−8M. The structural specificity of this site was probed by testing the competition between L-glutamate and various analogues for binding to cilia. The binding site is stereo-specific for L-glutamic acid, and requires the presence of all three ionizable groups on the glutamate molecule for optimal ligand: receptor interaction.