Figure 7.

Proposed mechanism for tRNA binding. The primarily binding of the dsRBD at the anticodon arm considered as a ‘reference point’ enables to measure the distance to the modification site. Then, the recruitment of the other modules via a flexible linker between the dsRBD and the helical domain operating as a molecular ruler enables the fine-tuned positioning of the catalytic domain around the tRNA elbow. Finally, the catalytic domain flips out U20 from its initial position to the FMN binding pocket for catalysis.