Fig. 2: Snapshots of each catalytic step during Leu-AMP formation.

All protein structures are shown as cartoon representations whereas ligands and interacting protein residues are shown as sticks. All H-bonds and salt bridges are shown as black dashed lines. A magnesium ion is shown as a gray sphere while its coordinating water molecules are shown as small red spheres. All structural domains are colored as shown in Fig. 1c. Substrates ATP (cyan), Leu (yellow), Leu analog l-leucinol (salmon), and the reaction intermediate Leu-AMP (orange) are shown as sticks. The NgLeuRS·ATP·leucinol ternary complex mimics the pre-transition state where both ATP and Leu are bound in the productive conformation in the aminoacylation site.