Fig. 2. Cryo-EM structure of Elp123 bound to tRNA^Ala_UGC.

(A) EMSA assay using endogenous Elp123 (left), recombinant Elongator (right), and fluorescently labeled tRNA^Ala_UGC in the presence of different concentrations of glutaraldehyde. The positions of free tRNA and protein-tRNA complexes (*) are indicated next to the native polyacrylamide gel electrophoresis (PAGE). (B) Representative microscale thermophoresis measurements, respective fits, and calculated dissociation constant (K_d) values for Elp123 (blue) and Elongator (green). In both cases, the Hill coefficient is close to 1, indicating the presence of independent binding sites. n = 3. (C) Atomic model of Elp123 lobe bound to tRNA (Elp1, orange; Elp2, yellow; Elp3, violet) showing additional electron density for tRNA at a resolution of 4.4 Å. The fitted tRNA^Ala_UGC model is colored in accordance to the scheme on the right [purple, acceptor stem (Acc); red, D-loop (DL); blue, ASL; orange, variable loop (VL); green, T-loop (TL)]. Close-up view highlighting the phosphate backbone of the VL and ASL following the density (bottom right). (D) Atomic model of Elp123-tRNA from different perspectives.