Id	Element	Ion	Binding family	Amino acids or nucleotide residues names	All bound residues	Is homomer	Number of bound amino acids or nucleotide residues	Number of all bound residues	Number of coordinating chains	Representative
3NBK-NI-1	NI	Ni²⁺	D2H2R2	ARG.ASP.HIS.	ARG.ASP.HIS.HOH.	✔	6	7	2	✔
3NBK-NI-2	NI	Ni²⁺	D2H2R2	ARG.ASP.HIS.	ARG.ASP.HIS.HOH.	✔	6	7	2	✘
3NBK-NI-3	NI	Ni²⁺	D2H2R2	ARG.ASP.HIS.	ARG.ASP.HIS.HOH.	✔	6	7	2	✘