GTPase component of the GTPBP3-MTO1 complex that catalyzes the 5-taurinomethyluridine (taum(5)U) modification at the 34th wobble position (U34) of mitochondrial tRNAs (mt-tRNAs), which plays a role in mt-tRNA decoding and mitochondrial translation (PubMed:29390138, PubMed:33619562). Taum(5)U formation on mammalian mt-tRNA requires the presence of both GTPBP3-mediated GTPase activity and MTO1 catalytic activity (PubMed:29390138). {ECO:0000269|PubMed:29390138, ECO:0000269|PubMed:33619562}. This is the function of Ensembl gene identifier ENSG00000130299 (GTPBP3, GTP binding protein 3, mitochondrial).