Project Summary Ribosomally synthesized and post-translationally modified peptides (RiPPs) constitute a large class of natural products with a wide range of biological activities, including anticancer, antinociceptive, antiplasmodial, and antibacterial. The biosynthetic enzymes that convert linear, inactive peptide substrates into constrained bioactive compounds are not well understood, especially with regards to enzyme mechanism, substrate recognition and in their utility for producing new derivatives. The Nair research group has been engaged in research to address these questions for the past 18 years. We seek to carry out biochemical, structural biological, and engineering studies on several classes of RiPP biosynthetic enzymes and address questions regarding substrate recognition, and substrate tolerance. We anticipate that this work will be of use not only towards the discovery of new therapeutic compounds but to enable the production of both of improved versions of these bioactive compounds, as well as new to enable production of peptide-based compounds for which the biosynthetic pathways are not known.