Impact of a stereocentre inversion in cyclic lipodepsipeptides from the viscosin group: a comparative study of the viscosinamide and pseudodesmin conformation and self-assembly.

The viscosin group covers a series of cyclic lipodepsipeptides (CLPs) produced by Pseudomonas bacteria, with a range of biological functions and antimicrobial activities. Their oligopeptide moieties are composed of both L- and D-amino acids. Remarkably, the Leu5 amino acid-centrally located in the nonapeptide sequence-is the sole residue found to possess either an L or D configuration, depending on the producing strain. The impact of this D/L switch on the solution conformation was investigated by NMR-restrained molecular modelling of the epimers pseudodesmin A and viscosinamide A. Although the backbone fold remained unaffected, the D/L switch adjusted the segregation between hydrophobic and hydrophilic residues, and thus the amphipathicity. It also influenced the self-assembly capacity in organic solvents. Additionally, several new minor variants of viscosinamide A from Pseudomonas fluorescens DR54 were identified, and an NMR assay is proposed to assess the presence of either an L- or D-Leu5.