Formation of ion-selective channel using cyclic tetrapeptides

It is important for ion channel peptides to have energetic stability and ion-selectivity for development of some medicines. In the present study, our objective was to achieve formation of energetically stable and ion-selective channels in the membrane using cyclic tetrapeptides. We succeeded in formation of energetically stable and ion-selective channels using two cyclic tetrapeptides cyclo(d-Ala-Dap)2 (Dap; l-2,3-diaminopropionic acid) and cyclo(d-Ala-Glu)2. The results of ion channel recording suggested that the cationic cyclo(d-Ala-Dap)2 was resulted in Cl− anion-selective and the anionic cyclo(d-Ala-Glu)2 led to K+ cation-selective ion channel formation, respectively. This ion selectivity may be attributed to the charge state of peptides. And a low-hydrophobic cyclic tetrapeptide; cyclo(d-Ala-Dap)2 had a tendency to form stable ion channel compared to more high-hydrophobic ones; cyclo(d-Phe-Lys)2, cyclo(d-Phe-Dap)2 and cyclo(d-Ala-Lys)2. Our findings will shed light on the field of ion channel peptide study, especially cyclic one.