Using the amber suppression approach, four noncanonical amino acids (ncAAs) were used to
replace existing amino acids at four positions in lasso peptide microcin J25 (MccJ25). The lasso
peptide biosynthesis enzymes tolerated all four ncAAs and produced antibiotics with efficacy
equivalent to wild-type in some cases. Given the rapid expansion of the genetically encoded ncAA
pool, this study is the first to demonstrate an expedient method to significantly increase the
chemical diversity of lasso peptides