CHARACTERIZATION OF A PRESYNAPTIC GLUTAMATE-RECEPTOR

Glutamate receptors mediate excitatory neurotransmission in the brain and are important in the formation of memory and in some neurodegenera tive disorders. A complementary DNA clone that encoded a 33-kilodalton protein (GR33) was obtained by screening a library with an antibody g enerated against glutamate binding proteins. The sequence of GR33 is i dentical to that of the recently reported presynaptic protein syntaxin . When GR33 was expressed in Xenopus oocytes, it formed glutamate-acti vated ion channels that are pharmacologically similar to those of N-me thyl-D-aspartate receptors but with different electrophysiological pro perties. Mutation of the leucine 278 residue in the single putative tr ansmembrane segment of GR33 affects the properties of the channel. Thu s, in vivo GR33 may be a presynaptic glutamate receptor.