Table 1.

Anomalous occupancy refinement values of K⁺ ions within the ion channel

Binding site	Residue ID	Anomalous refined occupancy [100 mM K+]	Anomalous peak height (σ)
A1	K1	0.23	28.50
A2	K2	0.25	30.03
A3	K3	0.28	35.67
A4	K4	0.27	36.74
B1	K1	0.22	36.66
B2	K2	0.24	36.74
B3	K3	0.26	39.37
B4	K4	0.30	38.63

Sites A₁ to A₄ occur within the A chain while sites B₁ to B₄ occur within the B chain. Each K⁺ ion within the selectivity filter is shared between four unit cells and thus has a maximum occupancy value of 0.25. Occupancy values >0.25 arise due to the correlation between atomic displacement parameter (B-factor) and occupancy