| 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 |
|---|---|---|---|---|---|---|---|---|---|---|
| 2HCK-CA-1 | CA | Ca²⁺ | E2X1 | GLU.PTR. | GLU.PTR. | ✔ | 3 | 3 | 2 | ✔ |
| 2HCK-CA-2 | CA | Ca²⁺ | E2X1 | GLU.PTR. | GLU.PTR. | ✔ | 3 | 3 | 2 | ✘ |
| 4EW9-CA-2 | CA | Ca²⁺ | E2X1 | AQA.GLU. | AQA.DGU.GLU.HOH. | ✘ | 3 | 5 | 2 | ✔ |
| 4EW9-CA-4 | CA | Ca²⁺ | E2X1 | AQA.GLU. | AQA.DGU.GLU.HOH. | ✘ | 3 | 5 | 2 | ✔ |