Fig. 1: The structure of TbADAT2/3 heterodimer bound to tRNA^Thr_CGU.

a Schematic representation of the protein subunits: ADAT2 CDA in salmon, ADAT3 N-terminal domain in blue, ADAT3^CDA in teal. Portions with traced atomic model as solid colors and non-resolved linkers as dotted lines. Important sequence motifs are annotated at their relative positions. Zn²⁺ coordinating residues are indicated by yellow triangles, the active-site glutamate / pseudo-active-site valine by a red and gray star, ‘gate’ residues of ADAT2 with a blue triangle. Conserved positive charges of the KR-motif annotated as blue “+“ signs. b Structural alignment of Tb, yeast and mouse ADAT2 and ADAT3 CDA domains and Staphylococcus aureus TadA. The sequences for human (Hs) ADAT2/3 included (MmADAT2/3 PDB: 7NZ7, scTAD2/3 PDB:7BV5, saTadA PDB: 2B3J). Structural elements of Tb are annotated (ADAT2 above, ADAT3 below) with α-helices as cylinders and β-sheets as arrows. Zn²⁺ coordinating residues are indicated by yellow triangles, the active-site glutamate / pseudo-active-site valine by a red and gray star, ‘gate’ residues of ADAT2 with a blue triangle and the active-site histidine of ADAT3 with a teal triangle. ADAT2^C is boxed in blue with annotation of the conserved positive charges of the KR-motif (“+“ signs). Grayed out letters indicate non-resolved loops in our structure and ADAT2^C residues not resolved in previous crystal structures. An ADAT3 conserved loop is annotated as a teal box. Other colors and boxes within the alignment represent relative conservation above 70%. c Four views of the final non-b-factor-sharpened cryoSPARC map that was used for modeling (presented at a level of 0.09) with atomic model. Colors as above. d Cartoon model of ADAT2/3 bound to tRNA. Colors as in 1 A. Zn²⁺ atoms in yellow, tRNA in black with only anticodon loop bases represented as slabs, the reactive C₃₄ nucleotide is annotated as C*. Gray arrows point to the ADAT3 N-terminal domain double linker.