Abstact

Biosynthetic modification of nonribosomal peptide backbones represents a potentially powerful strategy to modulate the structure and properties of an important class of therapeutics. Using a high-throughput assay for catalytic activity, we show here that an L-Phe-specific module of an archetypal nonribosomal peptide synthetase can be reprogrammed to accept and process the backbone-modified amino acid (S)-beta-Phe with near-native specificity and efficiency. A co-crystal structure with a non-hydrolysable aminoacyl-AMP analogue reveals the origins of the 40,000-fold alpha/beta-specificity switch, illuminating subtle but precise remodelling of the active site. When the engineered catalyst was paired with downstream module(s), (S)-beta-Phe-containing peptides were produced at preparative scale in vitro (~1 mmol) and high titres in vivo (~100 mg l(-1)), highlighting the potential of biosynthetic pathway engineering for the construction of novel nonribosomal beta-frameworks.