Enables PDZ domain binding activity and identical protein binding activity. Involved in regulation of presynapse assembly. Located in postsynaptic density and postsynaptic membrane. Is active in glutamatergic synapse and parallel fiber to Purkinje cell synapse. Is integral component of postsynaptic density membrane. Human ortholog(s) of this gene implicated in autosomal recessive spinocerebellar ataxia 18. Orthologous to human GRID2 (glutamate ionotropic receptor delta type subunit 2). [provided by Alliance of Genome Resources, Apr 2022]