Asp297 plays a key role in the substrate specificity of eEF2K. (A) Activities of selected eEF2K mutants against different concentrations of MH-1, as indicated. All assays were performed within the linear range of the assay. Data are means ± SEM. (B) Time course of WT and D297L against MH-1 at a low MH-1 concentration (50 μM). Data are means ± SEM (n = 3). (C) Activities of WT and D297L/V302K/R303A eEF2K against different concentrations of MH-1. All assays were performed within the linear range of the assay. Data are means ± SEM (n = 3).*, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.