8QEX

Streptavidin variant with a cobalt catalyst for CH metal-catalyzed hydrogen-atom-transfer (M-HAT)

Summary for 8QEX

• Entry DOI: 10.2210/pdb8qex/pdb
• Descriptor: Streptavidin, cobalt Streptavidin (3 entities in total)
• Functional Keywords: metal-catalyzed hydrogen-atom-transfer, artificial radical cyclase, protein design, metal binding protein
• Biological source: Streptomyces avidinii; More
• Total number of polymer chains: 2
• Total formula weight: 36487.62

Authors

Jakob, R.P.,Chen, D.,Ward, T.R. (deposition date: 2023-09-01, release date: 2024-07-31, Last modification date: 2024-10-16)

Primary citation

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.
An evolved artificial radical cyclase enables the construction of bicyclic terpenoid scaffolds via an H-atom transfer pathway.
Nat.Chem., 16:1656-1664, 2024

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.

PubMed: 39030420
DOI: 10.1038/s41557-024-01562-5

Experimental method

X-RAY DIFFRACTION (1.9 Å)