Conformational and self-assembly properties of cyclic lipodepsipeptides of the viscosin group

Cyclic lipodepsipeptides (CLPs) are secondary metabolites produced by various bacteria, most prominently Bacillus and Pseudomonas. These often display potential antimicrobial properties, frequently ascribed to the ability to disrupt cellular membranes or form ion-pores. CLPs are a structurally diverse group of molecules always consisting of an oligopeptide chain cyclized by a lacton bond and a fatty acid moiety. They are divided into several groups based on sequence similarity. One such group is the viscosin group, which contains CLPs produced by Pseudomonas that all feature nine amino acids and a conserved sequence pattern of hydrophobic and hydrophilic residues.1 Recently, we have extensively described the self-assembly properties of one viscosin group member, pseudodesmin A.2,3 We have shown that in non-polar organic solvents this CLP forms anisotropic supramolecular structures of unrestricted size, reminiscent of the ability to form ionpores in the non-polar cellular membrane environment. Here, we report on how the most prominent structural variations within the viscosin group affect the conformation and self-assembly properties. Since the well-defined monomer conformation of pseudodesmin A is key to this self-assembly, the most striking variation within the viscosin group is the variability of the Leu5 stereochemistry. For the first time, a conformational study will be reported for CLPs featuring an L-Leu5 residue, such as viscosin and viscosinamide. The results of this study contribute to a deeper understanding of the structure-function relationship of CLPs in general.