Life Science > Proteomics > Protein Chromatography > Affinity Chromatography
CNG channels do not discriminate between Na + and K + ions, and they also allow Ca 2+ and Mg 2+ to pass through, although at a slower rate. The passage of these divalent ions inhibit the current carried by Na + and K + . A highly conserved residue of glutamic acid in the selectivity filter of CNG channels has been found to form a high-affinity binding site for Ca 2+ . Moreover, a bacterial nonselective cation channel called the NaK channel hosts a selectivity filter sequence similar to that of CNG channels. In the crystal structure of the NaK channel, a discrete Ca 2+ -binding site at the extracellular opening of the pore has been identified.