Download MendeleyAn evolved artificial radical cyclase enables the construction of bicyclic terpenoid scaffolds via an H-atom transfer pathway.
Chen, D., Zhang, X., Vorobieva, A.A., Tachibana, R., Stein, A., Jakob, R.P., Zou, Z., Graf, D.A., Li, A., Maier, T., Correia, B.E., Ward, T.R.(2024) Nat Chem
- PubMed: 39030420
- DOI: https://doi.org/10.1038/s41557-024-01562-5
- Primary Citation of Related Structures:
8QEX - PubMed Abstract:
While natural terpenoid cyclases generate complex terpenoid structures via cationic mechanisms, alternative radical cyclization pathways are underexplored. The metal-catalysed H-atom transfer reaction (M-HAT) offers an attractive means for hydrofunctionalizing olefins, providing access to terpenoid-like structures. Artificial metalloenzymes offer a promising strategy for introducing M-HAT reactivity into a protein scaffold. Here we report our efforts towards engineering an artificial radical cyclase (ARCase), resulting from anchoring a biotinylated [Co(Schiff-base)] cofactor within an engineered chimeric streptavidin. After two rounds of directed evolution, a double mutant catalyses a radical cyclization to afford bicyclic products with a cis-5-6-fused ring structure and up to 97% enantiomeric excess. The involvement of a histidine ligation to the Co cofactor is confirmed by crystallography. A time course experiment reveals a cascade reaction catalysed by the ARCase, combining a radical cyclization with a conjugate reduction. The ARCase exhibits tolerance towards variations in the dienone substrate, highlighting its potential to access terpenoid scaffolds.
Organizational Affiliation:
Department of Chemistry, University of Basel, Basel, Switzerland.
