Neuron 2000 Mar 01;253:683-94. doi: 10.1016/s0896-6273(00)81070-3.

Four residues of the extracellular N-terminal domain of the NR2A subunit control high-affinity Zn2+ binding to NMDA receptors.

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NMDA receptors are allosterically inhibited by Zn2+ ions in a voltage-independent manner. The apparent affinity for Zn2+ of the heteromeric NMDA receptors is determined by the subtype of NR2 subunit expressed, with NR2A-containing receptors being the most sensitive (IC50, approximately 20 nM) and NR2C-containing receptors being the least sensitive (IC50, approximately 30 microM). Using chimeras constructed from these two NR2 subtypes, we show that the N-terminal LIVBP-like domain of the NR2A subunit controls the high-affinity Zn2+ inhibition. Mutations at four residues in this domain markedly reduce Zn2+ affinity (by up to >500-fold) without affecting either receptor activation by glutamate and glycine or inhibition by extracellular protons and Ni2+ ions, indicating that these residues most likely participate in high-affinity Zn2+ binding.

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Species referenced: Xenopus
Genes referenced: grin2a grin2c nodal2