Potassium channel

The central pore is filled with water which allows potassium ions to remain hydrate, Three potassium binding sites each provided from main chain C=O groups. Selectivity filter = Formed from conserved sequence residues 75-79, 75-78 bind potassium in two positions, third ion in cavity. Peptide bond carbonyl groups provide rings of O atoms Electrostatic repulsion ensures high movement throughout