The binding of potassium ions changes shape of the protein and results in their release outside the cell.

Phosphorylation leads to a change in protein shape, reducing its affinity for potassium ions, which is released outside the cell.

The binding of potassium ions changes shape of the protein and results in sodium ions binding simultaneously.

The protein simultaneously picks up sodium ions and they dislodge the potassium ions inside the cell.

Potassium ions are released into the cell.