The solution structure of uperin 3.6, an antibiotic peptide from the granular dorsal glands of the Australian toadlet, Uperoleia mjobergii

Uperin 3.6 (GVIDA(5)AKKVV(10)NVLKN(15)LF-NH2) is a wide-spectrum antibiotic peptide isolated from the Australian toadlet, Uperoleia mjobergii. With only 17 amino acid residues, it is smaller than most other wide-spectrum antibiotic peptides isolated from amphibians. In 50% (by vol.) trifluoroethanol, an NMR study and structure calculations indicate that uperin 3.6 adopts a well-defined amphipathic a-helix with distinct hydrophilic and hydrophobic faces. Examination of the activities of synthetic modifications of uperin 3.6 reveal that the three lysine residues are essential for antibiotic activity.