Investigation of selectivity and conduction mechanism in non-selective cation NaK channel using a combination of solid-state NMR spectroscopy and molecular dynamics simulations

Most of biological processes require the participation of specific cations, such as Na+, K+, H+, Ca2+ and Mg2+. Discrimination of different ions through the cell with high fidelity is mainly controlled by ion channels that are embedded in membranes. Until now, best understood ion channels are bacterial mono-cation channels, e.g. KcsA and NaK. They have been used as model systems to illustrate and clarify fundamental physical principles governing ion selectivity in ion channels [1]. Interestingly, although NaK and KcsA share high sequence similarity in the selectivity filter region, they yet exhibit drastically different ion selectivity. KcsA is a highly selective potassium channel, while NaK conducts potassium and sodium with equal efficiency [2,3].