Cyclic Peptides from Graspetide Biosynthesis and Native Chemical Ligation.
Choi, B., Acuna, A., Link, A.J.(2024) J Am Chem Soc 146: 11605-11609
- PubMed: 38634647 
- DOI: https://doi.org/10.1021/jacs.4c02745
- Primary Citation of Related Structures:  
8VYC - PubMed Abstract: 
The ribosomally synthesized and post-translationally modified peptide (RiPP) superfamily of natural products includes many examples of cyclic peptides with diverse macrocyclization chemistries. The graspetides, one family of macrocyclized RiPPs, harbor side chain-side chain ester or amide linkages. We recently reported the structure and biosynthesis of the graspetide pre-fuscimiditide, a 22-amino-acid (aa) peptide with two ester cross-links forming a stem-loop structure. These cross-links are introduced by a single graspetide synthetase, the ATP-grasp enzyme ThfB. Here we show that ThfB can also catalyze the formation of amide or thioester cross-links in prefuscimiditide, with thioester formation being especially efficient. We further show that upon proteolysis to reveal an N-terminal cysteine residue, the thioester-linked peptide rapidly and quantitatively rearranges via native chemical ligation into an isopeptide-bonded head-to-tail cyclic peptide. The solution structure of this rearranged peptide was determined by using 2D NMR spectroscopy experiments. Our methodology offers a straightforward recombinant route to head-to-tail cyclic peptides.
Organizational Affiliation: 
Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States.