4XWF:
reference: Metal Ion-Mediated Nucleobase Recognition by the ZTP Riboswitch., Trausch JJ, Marcano-Velazquez JG, Matyjasik MM, Batey RT, Chem Biol. 2015 Jul 23;22(7):829-37. doi: 10.1016/j.chembiol.2015.06.007. Epub, 2015 Jul 2. PMID: 26144884

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