A previously undescribed hexapeptide His-Arg-Phe-Leu-Arg-His-NH2 from amphibian skin secretion shows CO2 and metal biding affinities

[Display omitted] A novel six-residue peptide has been identified from the skin secretion of an amphibian. Structures of the peptide free and in the presence of CO2 and metals have been determined by NMR. It was possible to observe that the gas and the metals caused a variation in the peptide structure. •Identification of a HRFLRH peptide from Phyllomedusa centralis skin secretion.•Evidences of interaction of the peptide with CO2, Zn and Cd by Mass Spectroscopy.•NMR structural investigations of the peptide in the presence of CO2 and the metals. A previously undescribed six residues long peptide His-Arg-Phe-Leu-Arg-His was identified and purified from the skin secretion of the amphibian Phyllomedusa centralis. A synthetic analogue carboxyamidated HRFLRH-NH2 showed structural changes induced by CO2 and metal ions in aqueous solution when analyzed by NMR. The present work reports NMR structures for the carboxyamidated hexapeptide in the presence CO2, Zn2+ and Cd2+, suggesting possible affinity regions on the polypeptide chain for each ligand. The NMR structures were optimized by DFT to identify probable biding sites of these species in the polypeptide structure. To our best knowledge, this is the first time that a putative CO2 binding site is described on a peptide structure obtained in aqueous conditions, at room temperature.