8yj4

The complex structure of SdnG with its analogue of substrate

spinqualitylabelsall models 8yj4, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 8yj4 is a 6 chain structure with sequence from Sordaria araneosa. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.2Å Ligands: A1LYT Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function SDNG_SORAA Publication Abstract from PubMed Iminium-catalyzed cycloaddition is one of the most prominent examples of organocatalysis, yet a biological counterpart has not been reported despite the wide-spread occurrence of iminium adducts in enzymes. Here, we present biochemical, structural, and computational evidence for iminium catalysis by the natural Diels-Alderase SdnG that catalyzes norbornene formation in sordarin biosynthesis. A Schiff base adduct between the epsilon-nitrogen of active site K127 and the aldehyde group of the enal dienophile was revealed by structural analysis and captured under catalytic conditions via borohydride reduction. This Schiff base adduct positions the substrate into near-attack conformation and decreases the transition state barrier of Diels-Alder cyclization by 8.3 kcal/mol via dienophile activation. A hydrogen bond network consisting of a catalytic triad is proposed to facilitate proton transfer required for iminium formation. This work establishes a new mode of catalysis for Diels-Alderases and points the way to the design of novel iminium based (bio)catalysts. Iminium Catalysis in Natural Diels-Alderase.,Sun Z, Zang X, Zhou Q, Ohashi M, Houk KN, Zhou J, Tang Y Nat Catal. 2025 Mar;8(3):218-228. doi: 10.1038/s41929-025-01294-w. Epub 2025 Feb , 6. PMID:40881614 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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