TABLE 2

Summary of phenotypes at ligand-binding positions in NR1 and NR2.

Affinity and efficacy phenotypes for the 10 cysteine substitutions described in this article. The ID column tabulates the structural role of the mutated amino acids: LB1–LB5 are residues in which sidechains form hydrogen bonds with the bound ligand in the GluR2 crystal structure. The position labeled ′lid′ sterically prevents the bound ligand from leaving the closed cleft conformation. The amino acid labeled ′bb′ forms an H-bond between its backbone carbonyl oxygen and the bound ligand. The position labeled ′i′ refers to a residue at the interlobe interface. For each position, the following information is tabulated: which compound was a full agonist at the Gly site (in NR1) or glutamate site (in NR2A); which partial agonists were used; the fold-change in affinity constant KA and efficacy constant E (mean ± S.E.M., P-value). Significant P-values (P < 0.05) are shown in bold. The rightmost column lists which phenotype was found.

Agonist Fold Change KA Fold Change E
Mutant ID Full Partial α N Mean ± S.E.M. P Mean ± S.E.M. P Role
Wild-type Gly DCS 0.81 9 -1.2 ± 0.6 0.23 -1.6 ± 0.7 0.061 N.A.
Gly d-Ser 4 1.2 ± 0.07 0.035 0.6 ± -1.6 0.039
l-Glu l-Asp 0.91 6 -2.9 ± 0.7 0.03 -3.6 ± 1.2 0.04 N.A.
l-Glu NMDA 0.79 5 -1.3 ± 0.9 0.21 -1.8 ± 0.5 0.155 N.A.
NR1 T518C LB1 Gly DCS 0.44 9 -3.0 ± 0.6 0.002 -17.2 ± 5.2 0.000 A,E
d-Ser 0.81 12 22.8 ± 6.2 0.008 1.0 ± 0.7 0.770 A
NR1 R523C LB2 d-Ser DCS 0.88 7 -2.1 ± 0.2 0.008 -17.0 ± 4.3 0.0004 A,E
Gly 0.76 4 -17.1 ± 5.6 0.04 -29.7 ± 13.1 0.04 A,E
NR1 V689C LB4 Gly DCS 0.75 5 -4.3 ± 0.4 0.0003 -51.5 ± 7.2 0.0004 A,E
d-Ser 0.88 3 -7.6 ± 0.6 0.002 -273 ± 67 0.002 A,E
NR1 D732C LB5 Gly DCS 0.88 3 -87.3 ± 57.5 0.0001 -9.9 ± 4.0 0.001 A,E
d-Ser 0.81 8 -10.0 ± 5.1 0.002 -3.3 ± 0.5 0.010 A,E
NR2A T513C LB1 l-Glu NMDA 0.91 5 1.5 ± 0.6 0.03 -5.1 ± 0.7 0.022 A,E
NR2A R518C LB2 l-Glu d-Glu 0.01 4 -5.3 ± 2.4 0.04 1.7 ± 0.1 0.004 A,E
NR2A T690C LB4* l-Asp l-Glu 0.90 6 -11.8 ± 2.0 0.003 -213 ± 54 0.001 A,E
NR1 I691C i Gly DCS 0.94 4 1.2 ± 1.2 0.55 -23.4 ± 0.0 0.001 E
NR2A H485C lid l-Glu NMDA 0.46 3 -2.0 ± 0.7 0.35 -11.3 ± 3.0 0.010 E
NR2A S511C bb l-Glu l-Asp 0.47 7 -2.1 ± 0.2 0.52 -20.6 ± 3.6 0.023 E
  • A, affinity, E, efficacy, N.A., not applicable.