# Expanding the Range of Darobactin Derivatives by Amber Stop Codon Suppression To Introduce Non-canonical Amino Acids

## TL;DR

Scientists modified a promising antibiotic called darobactin by adding special amino acids to improve its effectiveness against bacteria.

## Contribution

A new method using amber stop codon suppression to introduce non-canonical amino acids into darobactin derivatives is presented.

## Key findings

- Darobactin A F7F, with a fluorine-substituted phenylalanine, was successfully synthesized and validated by NMR.
- The new derivative showed antimicrobial activity comparable to darobactin A against Gram-negative bacteria.

## Abstract

The ribosomally synthesized and post-translationally
modified peptide
(RiPP) darobactin A is a promising new antibiotic candidate with anti-Gram-negative
activity inflicted by the inhibition of the novel target BamA. Genome
mining revealed many putative darobactin producer strains, but a limited
number of compound modification options. In this study, the amber
stop codon suppression technique was used to integrate non-canonical
amino acids into the bicyclic heptapeptide, creating new darobactin
derivatives. The C-terminal phenylalanine was replaced by non-canonical
phenylalanine derivatives with different substituents. Darobactin
A F7F, featuring a fluorine atom in the para position of the C-terminal
phenylalanine, was purified to enable structure validation by NMR.
Activity assays revealed antimicrobial potency against selected Gram-negative
strains comparable to darobactin A.