Structure of the MazF-mt9 toxin, a tRNA-specific endonuclease from Mycobacterium tuberculosis

Tuberculosis (TB) is a severe disease caused by Mycobacterium tuberculosis (M. tb) and the well-characterized M. tb MazE/F proteins play important roles in stress adaptation. Recently, the MazF-mt9 toxin has been found to display endonuclease activities towards tRNAs but the mechanism is unknown. We hereby present the crystal structure of apo-MazF-mt9. The enzyme recognizes tRNA^Lys with a central UUU motif within the anticodon loop, but is insensitive to the sequence context outside of the loop. Based on our crystallographic and biochemical studies, we identified key residues for catalysis and proposed the potential tRNA-binding site.