Figure 6.
The dimer interface of the GluN1-NTD dimer. A, Surface representation of the two protomers of the GluN1-NTD that form a dimer. The colored surface represents residues in the buried dimer interface. Red and orange represent residues within the interface that make specific side chain interactions. Residue contacts are represented as connected lines. Solid black lines represent hydrophobic side chain interactions, while dotted lines represent polar or ionic interactions. Red (Y109) and green (T110) represent residues that were mutated in this study. The total buried surface area of the GluN1-NTD at the dimer interface has ∼1000 Å2, which is comparable to the mGluR1-LBD (∼900 Å2) (Kunishima et al., 2000) but not as large as the GluK2 (Kumar et al., 2009) and GluA2-NTD (Jin et al., 2009) (∼1500 Å2), whose dimer interfaces are equally distributed among the R1 and R2 domains. B, The dimer structures of the GluN1-NTD, GluA2-NTD (Protein Data Bank identifier 3H5V), and mGluR1-LBD (Protein Data Bank identifier 1EWT) are shown after aligning one of the R1 subdomains of each structure. Arrow indicates the aligned R1 subdomain. The R1 and R2 subdomains of each NTD are color-coded as in Figure 5. The helices α2 and α3 are labeled. Note the relative orientation of the R2 domains is unique in each NTD dimer. As a result, the global positioning of the R1 subdomains is highly divergent in each NTD dimers.