Solution structure of polytheonamide B, a highly cytotoxic nonribosomal polypeptide from marine sponge

NMR spectroscopy, structure calculation and energy minimization are applied to determine the three-dimensional structure of polytheonamide B (pTB), a highly cytotoxic polypeptide which is one of the most unusual nonribosomal peptides of sponge origin. The pTB molecules are found to form transmembrane channels that permeate monovalent cations similar to gramicidin A channels and the strong cytotoxicity of pTB could be attributed to its ability to form single molecule channels through biological membranes.