Staurosporine isolated from Streptomyces sp. TP-A0274 is a member of the family of indolocarbazole alkaloids that exhibit strong antitumor activity. A key step in staurosporine biosynthesis is the formation of the indolocarbazole core by intramolecular C–C bond formation and oxidative decarboxylation of chromopyrrolic acid (CPA) catalyzed by cytochrome P450 StaP (StaP, CYP245A1). In this study, we report x-ray crystal structures of CPA-bound and -free forms of StaP. Upon substrate binding, StaP adopts a more ordered conformation, and conformational rearrangements of residues in the active site are also observed. Hydrogen-bonding interactions of two carboxyl groups and T-shaped π–π interactions with indole rings hold the substrate in the substrate-binding cavity with a conformation perpendicular to the heme plane. Based on the crystal structure of StaP–CPA complex, we propose that C–C bond formation occurs through an indole cation radical intermediate that is equivalent to cytochrome c peroxidase compound I [Sivaraja M, Goodin DB, Smith M, Hoffman BM (1989) Science 245:738–740]. The subsequent oxidative decarboxylation reaction is also discussed based on the crystal structure. Our crystallographic study shows the first crystal structures of enzymes involved in formation of the indolocarbazole core and provides valuable insights into the process of staurosporine biosynthesis, combinatorial biosynthesis of indolocarbazoles, and the diversity of cytochrome P450 chemistry.

Ultraviolet-protective compounds, such as mycosporine-like amino acids (MAAs) and related gadusols produced by some bacteria, fungi, algae, and marine invertebrates, are critical for the survival of reef-building corals and other marine organisms exposed to high-solar irradiance. These compounds have also been found in marine fish, where their accumulation is thought to be of dietary or symbiont origin. In this study, we report the unexpected discovery that fish can synthesize gadusol de novo and that the analogous pathways are also present in amphibians, reptiles, and birds. Furthermore, we demonstrate that engineered yeast containing the fish genes can produce and secrete gadusol. The discovery of the gadusol pathway in vertebrates provides a platform for understanding its role in these animals, and the possibility of engineering yeast to efficiently produce a natural sunscreen and antioxidant presents an avenue for its large-scale production for possible use in pharmaceuticals and cosmetics.

Goadsporin (GS) is a member of ribosomally synthesized and post-translationally modified peptides (RiPPs), containing an N-terminal acetyl moiety, six azoles and two dehydroalanines in the peptidic main chain. Although the enzymes involved in GS biosynthesis have been defined, the principle of how the respective enzymes control the specific modifications remains elusive. Here we report a one-pot synthesis of GS using the enzymes reconstituted in the ‘flexible’ in vitro translation system, referred to as the FIT–GS system. This system allows us to readily prepare not only the precursor peptide from its synthetic DNA template but also 52 mutants, enabling us to dissect the modification determinants of GodA for each enzyme. The in vitro knowledge has also led us to successfully produce designer GS analogues in vivo. The methodology demonstrated in this work is also applicable to other RiPP biosynthesis, allowing us to rapidly investigate the principle of modification events with great ease.