2XC9:
reference: Metal-ion dependence of the active-site conformation of the translesion DNA polymerase Dpo4 from Sulfolobus solfataricus., Irimia A, Loukachevitch LV, Eoff RL, Guengerich FP, Egli M, Acta Crystallogr Sect F Struct Biol Cryst Commun. 2010 Sep 1;66(Pt, 9):1013-8. Epub 2010 Aug 21. PMID: 20823515

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