The preference of the mitochondrial endonuclease for a conserved sequence block in mitochondrial DNA is highly conserved during mammalian evolution.

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RESUMO

Endonuclease activity identified in crude preparations of rat and human heart mitochondria has each been partially purified and characterized. Both the rat and human activities purify as a single enzyme that closely resembles the endonuclease of bovine-heart mitochondria (Cummings, O.W. et. al. (1987) J. Biol. Chem. 262:2005-2015). All three enzymes, for example elute similarly during gel filtration and DNA-cellulose chromatography, and exhibit similar enzymatic properties. Although the nucleotide sequences of the mtDNAs indicate that there has occurred an unusual degree of divergence in the displacement-loop region during mammalian evolution, the nucleotide specificities of the mt endonucleases appear highly conserved and show a striking preference for an evolutionarily-conserved sequence tract that is located upstream from the heavy (H)-strand origin of DNA replication (OriH).

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