Gausemycins A,B – Cyclic Lipoglycopeptides from Streptomyces Sp.

We report a novel family of natural lipoglycopeptides produced by Streptomyces sp. INA-Ac-5812. Two major components of the mixture, named gausemycins A and B, were isolated, and their structures were elucidated. The compounds are cyclic peptides with a unique peptide core and several remarkable structural features, including unusual positions of D-amino acids, lack of the Ca2+ -binding Asp-X-Asp-Gly (DXDG) motif, tyrosine glycosylation with arabinose, presence of 2-amino-4-hydroxy-4- phenylbutyric acid (Ahpb) and chlorinated kynurenine (ClKyn), N-acylation of the ornithine side chain. These major components of the peptide antibiotic family have pronounced activity against Gram-positive bacteria. The mechanism of action of gausemycins was explored by a number of methods, showing significant differences compared to glycopeptides and related lipopeptides. For example, gausemycins exhibit no Ca2+ -dependence of antimicrobial activity and induce no pore formation at low concentrations. Moreover, there is no detectable accumulation of cell wall biosynthesis precursors under treatment with gausemycins.