RT Journal Article
SR Electronic
T1 Molecular Determinants of Proton-Sensitive  <em>N</em>-Methyl-<span class="sc">d</span>-aspartate Receptor Gating
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 1212
OP 1222
DO 10.1124/mol.63.6.1212
VO 63
IS 6
A1 Low, Chian-Ming
A1 Lyuboslavsky, Polina
A1 French, Adam
A1 Le, Phuong
A1 Wyatte, Karen
A1 Thiel, William H.
A1 Marchan, Edward M.
A1 Igarashi, Kazuei
A1 Kashiwagi, Keiko
A1 Gernert, Kim
A1 Williams, Keith
A1 Traynelis, Stephen F.
A1 Zheng, Fang
YR 2003
UL http://molpharm.aspetjournals.org/content/63/6/1212.abstract
AB Extracellular protons inhibit N-methyl-d-aspartate (NMDA) receptors with an IC50 value in the physiological pH range. To identify the molecular determinants of proton sensitivity, we used scanning mutagenesis of the NR1 subunit to search for residues that control proton inhibition of NMDA receptors. Homology modeling of the extracellular domains suggested that residues at which mutations perturbed pH sensitivity were localized in discrete regions. The majority of mutations that strongly affected proton sensitivity were clustered in the extracellular end of the second transmembrane domain (M3) and adjacent linker leading to the S2 portion of the glycine-binding domain of NR1. Mutations in NR2A confirmed that the analogous region controls the pH sensitivity of this subunit and also identified the linker region between the third transmembrane domain (M4) and the S2 portion of the NR2 glutamate binding domain as an additional determinant of proton sensitivity. One mutant receptor, NR1(A649C)/NR2A(A651T), showed a 145-fold reduction in the IC50 for protons (IC50, 17.3 μM corresponding to pH 4.9). The M3-S2 linker region has been suggested to control NMDA receptor gating, leading to the hypothesis that the proton sensor and receptor gate may be structurally and functionally integrated.