4IEM:
reference: Conserved Structural Chemistry for Incision Activity in Structurally Non-homologous Apurinic/Apyirmidince Endonuclease APE1 and Endonuclease IV DNA repair enzymes., Tsutakawa SE, Shin DS, Mol CD, Izumi T, Arvai AS, Mantha AK, Szczesny B, Ivanov IN, Hosfield DJ, Maiti B, Pique ME, Frankel KA, Hitomi K, Cunningham RP, Mitra S, Tainer JA, J Biol Chem. 2013 Jan 25. PMID: 23355472

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