Figure 1. Strategy and prerequisites for the production of congeneric, ribosomally synthesized peptides in emancipated E. coli cells.

(a) Evolutionarily adapted E. coli cells are cultivated in defined minimal medium until residual Trp is consumed and cells solely grow on [3,2]Tpa. (b) The Trp (2) progenitor indole (1) is replaced by 4H-thieno[3,2-b]pyrrole (Tp) (3), which in turn is converted into [3,2]Tpa (4) by the tryptophan synthetase. (c) Scheme of the biosynthesis of Bliβ. The linear precursor peptide is translationally synthesized from the corresponding gene (indicated in black) (I). Dehydrations and thioether bridges are enzymatically installed (II–III) (residues depicted in light grey) and the modified peptide is exported via a specific transporter (IV). Extracellularly, a protease activates the peptide by removal of an N-terminal hexapeptide (V). Dhb, didehydrobutyrine; Dha, didehydroalanine; Obu, 2-oxobutyryl; Abu, aminobutyrate.