Cyclic lipoundecapeptide amphisin from Pseudomonas sp. strain DSS73.

The crystal structure of the lipoundecapeptide amphisin, presented here as the tetrahydrate, C(66)H(114)N(12)O(20).4H(2)O, originating from non-ribosomal biosynthesis by Pseudomonas sp. strain DSS73, has been solved to a resolution of 0.65 A. The primary structure of amphisin is beta-hydroxydecanoyl-D-Leu-D-Asp-D-allo-Thr-D-Leu-D-Leu-D-Ser-L-Leu-D-Gln-L-Leu-L-Ile-L-Asp (Leu is leucine, Asp is aspartic acid, Thr is threonine, Ser is serine, Gln is glutamine and Ile is isoleucine). The peptide is a lactone, linking Thr4 O(gamma) to the C-terminal. The stereochemistry of the beta-hydroxy acid is R. The peptide is a close analogue of the cyclic lipopeptides tensin and pholipeptin produced by Pseudomonas fluorescens. The structure of amphisin is mainly helical (3(10)-helix), with the cyclic peptide wrapping around a hydrogen-bonded water molecule. This lipopeptide is amphiphilic and has biosurfactant and antifungal properties.