Fig. 4: The effects of L550A and E169G mutants on NgLeuRS catalytic efficiency.
a Schematics of assays for Leu activation (top) and Leu transfer (bottom). The former is performed by ATP-PPi exchange assay to measure the effects of L550A and E169G mutants on Leu activation while the latter was used to evaluate the second stage Leu transfer to tRNALeu. b Upper panels: the relative position of the CP1 hairpin to the L550A-containing α-helix in the NgLeuRS-L550A mutant in different trapped catalytically states. Lower panels: zoom of the L550A region. The CP1 hairpin remains in the closed conformation following Leu-AMP formation. 2Fo-Fc electron density maps (gray mesh) are all countered at 1.5 σ. c Relative position of CP1 hairpin to the L550-containing α-helix in NgLeuRS-E169G mutant. The CP1 hairpin of the E169G mutant remains in an open conformation during Leu activation. Omit maps (gray mesh) of ligands are countered at 3.5–5 σ. In b, c the CP1 hairpin is shown as cartoon backbone representations while the L550-containing α-helix is a mixed cartoon and stick representation. The ligands are shown as sticks while the catalytic magnesium ion is shown as a gray sphere.
