FIGURE 5.

Receptor-bound substrate studied by torsion angle ssNMR measurements. (A) This image shows the structure of the receptor-bound Glu amino acid, based on X-ray crystallography (PDB 1FTJ) (Armstrong and Gouaux, 2000). Selected residues surrounding the bound substrate are indicated. (B) HCCH ssNMR analysis of χ₁ and χ₂ side chain angles enabled the measurement of the Glu residue structure while it was bound to the crystalline unlabeled protein (Edwards et al., 2010). This figure was prepared with UCSF ChimeraX (Pettersen et al., 2021).