Nocathioamides, Uncovered by a Tunable Metabologenomic Approach, Define a Novel Class of Chimeric Lanthipeptides

Discovery of a Unique Structural Motif in Lanthipeptide Synthetases for Substrate Binding and Interdomain Interactions

Class III lanthipeptide synthetases catalyze the formation of lanthionine/methyllanthionine and labionin crosslinks. We present here the 2.40 Å resolution structure of the kinase domain of a class III lanthipeptide synthetase CurKC from the biosynthesis of curvopeptin. A unique structural subunit for leader binding, named leader recognition domain (LRD), was identified. The LRD of CurKC is responsible for the recognition of the leader peptide and for mediating interactions between the lyase and kinase domains. LRDs are highly conserved among the kinase domains of class III and class IV lanthipeptide synthetases. The discovery of LRDs provides insight into the substrate recognition and domain organization in multidomain lanthipeptide synthetases.

Induction of Diverse Cryptic Fungal Metabolites by Steroids and Channel Blockers

Fungi offer a deep source of natural products but remain underutilized. Most biosynthetic gene clusters (BGCs) that can be detected are silent or "cryptic" in standard lab cultures and their products are thus not interrogated in routine screens. As genetic alterations are difficult and some strains can only be grown on agar, we have herein applied an agar-based high-throughput chemical genetic screen to identify inducers of fungal BGCs. Using R. solani and S. sclerotiorum as test cases, we report 13 cryptic metabolites in four compound groups, including sclerocyclane, a natural product with a novel scaffold. Steroids were the best elicitors and follow-up studies showed that plant-steroids trigger sclerocyclane synthesis, which shows antibiotic activity against B. plantarii, an ecological competitor of S. sclerotiorum. Our results open new paths to exploring the chemical ecology of fungal-plant interactions and provide a genetics-free approach for uncovering cryptic fungal metabolites.