In vivo production of thiopeptide variants.

Thiopeptides are a family of highly modified peptide metabolites, characterized by a macrocycle bearing a central piperidine/dehydropiperidine/pyridine ring, multiple thiazole rings, and several dehydrated amino acid residues. Thiopeptides have useful antibacterial, antimalarial, and anticancer properties but have not been adapted for human clinical applications, owing in part to their poor water solubility. In 2009, it was revealed that the thiopeptide scaffold is derived from a ribosomally synthesized precursor peptide subjected to extensive posttranslational modifications. Shortly thereafter, three groups developed two types of in vivo strategies to generate thiopeptide variants: precursor peptide mutagenesis and gene inactivation. The thiopeptide analogs and biosynthetic intermediates obtained from these studies provide much-needed insight into the biosynthetic process for these complicated metabolites. Furthermore, the in vivo production of variants can be employed to interrogate thiopeptide structure-activity relationships and may be useful to address the bioavailability issues plaguing these otherwise promising lead molecules. This chapter discusses the in vivo systems developed to generate thiopeptide variants.