Lysine Scanning of Arg(10)–Teixobactin: Deciphering the Role of Hydrophobic and Hydrophilic Residues

[Image: see text] Teixobactin is a recently discovered antimicrobial cyclodepsipeptide with good activity against Gram positive bacteria. Taking Arg(10)–teixobactin as a reference, where the nonproteinogenic residue l-allo-enduracididine was substituted by arginine, a lysine scan was performed to identify the importance of keeping the balance between hydrophilic and hydrophobic amino acids for the antimicrobial activities of this peptide family. Thus, the substitution of four isoleucine residues present in the natural sequence by lysine led to a total loss of activity. On the other hand, the substitution of the polar noncharged residues and alanine by lysine allowed us to keep and in some cases to improve the antimicrobial activity.