Figure 2.

NR3A and NR3B share structural homology with other members of the iGluR gene family but have a unique loop 1 structure. (A) Multiple sequence alignment of the S1 and S2 segments for the glycine-bound complexes of NR3A (2RC7), NR3B (2RCA), and NR1 (1PB7), the glutamate-bound complexes of NR2A (2A5S), GluR2 (1FTJ), and GluR0 (1II5), and the D-serine complex of the delta 2 subunit (2V3U), coloured by secondary structure. Drawn above the aligned sequence is the secondary structure of NR3A, with red and blue lines indicating the S1 and S2 peptides; conserved amino acids that interact with the ligand Cα functional groups are indicated by a asterisk; cysteine residues that form disulphide bonds are connected by green lines; a black line flanked by inverted triangles indicates loop 1; dots indicate regions for which no main-chain electron density was observed. (B) Stereo view of the same series of structures superimposed by least squares using domain 1 Cα coordinates. Loop 1 is drawn using a ribbon representation, with the remainder of the structure shown as a Cα trace; for NR3A, α-helices are drawn as transparent cylinders.