2NOO:
reference: Nickel binding to NikA: an additional binding site reconciles spectroscopy, calorimetry and crystallography., Addy C, Ohara M, Kawai F, Kidera A, Ikeguchi M, Fuchigami S, Osawa M, Shimada I, Park SY, Tame JR, Heddle JG, Acta Crystallogr D Biol Crystallogr. 2007 Feb;63(Pt 2):221-9. Epub 2007, Jan 16. PMID: 17242515

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