The function of Ensembl gene identifier ENSG00000198785 (GRIN3A, glutamate ionotropic receptor NMDA type subunit 3A) is as follows. Component of a non-conventional N-methyl-D-aspartate (NMDA) receptors (NMDARs) that function as heterotetrameric, ligand-gated cation channels with low calcium permeability and low voltage-dependent block by Mg(2+) (By similarity). During the development of neural circuits, participates in the synaptic refinement period, restricting spine maturation and growth (By similarity). Forms glutamatergic receptor complexes with GluN1 and GluN2 subunits which are activated by glycine binding to the GluN1 and GluN3 subunits and L-glutamate binding to GluN2 subunits (By similarity). Forms excitatory glycinergic receptor complexes with GluN1 alone which are activated by glycine binding to the GluN1 and GluN3 subunits (PubMed:38598639). GluN3A subunit also binds D-serine (By similarity). Each GluN3 subunit confers differential attributes to channel properties, including activation, deactivation and desensitization kinetics, pH sensitivity, Ca2(+) permeability, and binding to allosteric modulators (By similarity). By competing with GIT1 interaction with ARHGEF7/beta-PIX, may reduce GIT1/ARHGEF7-regulated local activation of RAC1, hence affecting signaling and limiting the maturation and growth of inactive synapses (By similarity). {ECO:0000250|UniProtKB:Q9R1M7, ECO:0000269|PubMed:38598639}.