A novel frog skin peptide containing function to induce muscle relaxation

► A member of a novel amphibian myotropic peptide family, polypedarelaxin 1, was purified from the tree frog, Polypedates pingbianensis. ► Polypedarelaxin 1 does not contain conserved structural motifs of other amphibian myotropic peptides. ► The signal peptide of polypedarelaxin 1 shows high sequence identity to that of other amphibian skin defensive peptides. ► Polypedarelaxin 1 was only found to exert contractile activity on isolated rat ileum smooth muscle.