Figure 1. Isoleucine side chain solution NMR spectra along the GCK reaction coordinate.

Crystal structures of GCK in (A) unliganded (PDB 1V4T), (B) glucose-bound (PDB 3IDH), and (C) glucose and AMP-PNP-bound forms (PDB 3FGU) depicting the location of isotopically labeled side chains used in this study. Ile Cα positions and tryptophan Cα side chains are depicted as red and yellow spheres, respectively. The large and the small domains are represented in gray and blue, respectively. β-hairpin/loop 151–179 is colored in magenta, glucose is in green, and AMP–PNP in orange. 2D ¹H-¹³C HMQC NMR spectra of Cδ1 methyl groups of (D) unliganded, (E) glucose-bound, and (F) glucose and AMP–PNP-bound forms of GCK. Assignments of Ile residues in the large domain are in gray with label “L,” Ile residues in the small domain are in blue with label “S,” and Ile residues in the 151–179 loop are in magenta. The average Ile Cδ1 chemical shift of intrinsically disordered Ile side chains deposited in the BMRB database is displayed as an open red circle in Figure 1D (for more details, see Figure S4).