How is this problem actually fixed? Well, it turns out that if we zoom in on this section, so let's suppose one of these potassium ions makes its way into this region and it loses these water molecules. So what exactly happens to that potassium ion as it travels through this section? Well, within this restricted region of the cavity, we basically have a five amino acid sequence known as a selectivity filter on each side of that potassium ion. So one on the left side and one on the right side. So we have the sequence of three anion, valine, glycine, tyrosine, and glycine on this side as well as on this side.