Figure 4. Interactions around the tRNA scissile bond and the ELAC2 HFSQRY motif.

(A) In the RNAse Z-HS structure, the 3′-oxygen interacts with a Zn²⁺ after the 3′-trailer is removed (B) Composite cryo-EM density of the human mitochondrial RNase Z bound to the mt-tRNA^His-Ser(AGY) precursor, carrying the ELAC2 mutation H548A. The part of the map corresponding to mt-tRNA^Ser(AGY) moiety was gaussian-filtered with a B-factor of 600 in UCSF ChimeraX. Colored as in Fig. 1. (C) The RNase Z^H548A-HS structure shows how the scissile bond is well-oriented for catalysis assisted by K700. The missing Zn²⁺ due to the H548A mutation is shown by a transparent circle based on the RNase Z-HS structure. In the RNase Z-HS structure, the 3′-oxygen interacts with a Zn²⁺ after the 3′-trailer is removed.