Schematic representation of nucleotide binding domain of Gtr1 with bound GMPPNP, derived from the X-ray crystal structure of the Gtr1-Gtr2 complex (PDB id: 3R7W). Switch I and II regions are shown in green and red, respectively. The side chains of Arg37 and Val67 are shown in blue and red, respectively. The positions of tryptophan residues are shown as Trp60 (red), and Trp167 and 175 (blue). Bound Mg2+ is shown in orange. The molecular graphic image was generated using PyMOL.