. 2019 Apr 25;20(8):2041. doi: 10.3390/ijms20082041

Table 1.

Features of the four topoisomerases in mammalian mitochondria.

Features	Top1mt	Top2α	Top2β	Top3α
Classification	Type IB	Type IIA	Type IIA	Type IA
Shown mitochondrial function	Regulation of transcription [56,57] and replication [58]		Regulation of replication [38]	Decatenation of hemicatenates [59]
Potential mitochondrial functions	Regulation of translation [59]	Scaffolding of the non-coding region, 7S protection [56]	Decatenation, recombination	Recombination, replication
Encoding details	Mitochondria-specific gene [60]	Probably identical to nuclear protein	Probably identical to nuclear protein	Alternative start codon [46]
Mitochondrial targeting sequence	Yes [60]	Unknown	Unknown	Yes [46]
Enzyme structure	Monomer	Homodimer	Homodimer	Monomer
Cofactors	Stimulated by Mg²⁺ or Ca²⁺ [60]	Mg²⁺, ATP	Mg²⁺, ATP	Mg²⁺
Protein size	70 kDa	174 kDa	180 kDa	110 kDa