Figure 1:

The discovery of graspetides as ribosomally synthesized and post-translationally modified peptides (RiPPs). A: Cartoons depicting the connectivity of (left) marinostatin and (right) microviridin. The ω-ester and ω-amide linkages are colored teal and maroon, respectively. B: The mdn biosynthetic gene cluster (BGC) for microviridin B and the mvd BGC for microviridin K. C: The mechanism of ω-ester or ω-amide linkage formation by a graspetide-associated ATP-grasp enzyme. X represents oxygen or nitrogen from a Ser, Thr, or Lys donor residue. D: Schematics for modifying the C-terminal core peptide (teal) of a graspetide precursor with ATP-grasp enzyme, which requires the leader peptide (pink).