Cation Selectivity of Membrane Proteins

Abstract

Abstract In order to investigate the high‐affinity K + binding to proteins, alkali ion binding studies were performed on a fluorescent derivative of membrane‐bound Na,K‐ATPase in buffered aqueous solution at 37°C employing a specially designed automatic spectrofluorometric titration system. The comparison of the obtained apparent stability constants, which reached values for K + even over 10 4 M −1 with those of a simpler cyclic peptide, acting as a suitable model compound, provides suggestions concerning the molecular nature of the binding sites involved.