N-terminal leucine/isoleucine/valine-binding protein (LIVBP)-like domain of the delta1 receptor of an orphan glutamate receptor family
N-terminal leucine/isoleucine/valine-binding protein (LIVBP)-like domain of the delta1 receptor of an orphan glutamate receptor family. While this N-terminal domain belongs to the periplasmic-binding fold type I superfamily, the glutamate-binding domain of the iGluR is structurally homologous to the periplasmic-binding fold type II. The LIVBP-like domain of iGluRs is thought to play a role in the initial assembly of iGluR subunits, but it is not well understood how this domain is arranged and functions in intact iGluR. Although the delta receptors are a member of the ionotropic glutamate receptor family, they cannot be activated by AMPA, kainate, NMDA, glutamate, or any other ligands. Phylogenetic analysis shows that both GluRdelta1 and GluRalpha2 may be closer related to non-NMDA receptors. In contrast to GluRdelta2, GluRdelta1 is expressed in many areas in the developing CNS, including the hippocampus and the caudate putamen. Furthermore, recent studies have shown that the orphan GluRdelta1 plays an essential role in high-frequency hearing and ionic homeostasis in the basal cochlea and that the locus encoding GluRdelta1 may be involved in congenial or acquired high-frequency hearing loss in humans.