MT-TK

MT-TK encodes mitochondrial tRNA-Lys, one of the 22 transfer RNAs encoded by mitochondrial DNA. After excision from the polycistronic mtDNA transcript and post-transcriptional maturation, it is charged with lysine by the corresponding mitochondrial aminoacyl-tRNA synthetase and, in the mitochondrial matrix, acts as the adaptor that reads the lysine codons AAA and AAG (AAR) of the 13 mtDNA-encoded mRNAs on the mitoribosome, delivering lysine to the growing polypeptide. Its anticodon wobble uridine carries a taurine-containing modification; the MERRF-associated m.8344A>G variant abolishes this modification and the unmodified tRNA cannot translate either lysine codon. Pathogenic variants in MT-TK, like those in other mt-tRNA genes, impair mitochondrial translation and oxidative phosphorylation and cause maternally inherited mitochondrial disease.