4u2l

Dithionite reduced cholesterol in complex with sulfite

spinqualitylabelsall models 4u2l, resolution 1.34Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4u2l is a 1 chain structure. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: SFD, SO4 Related: 4u2t, 4u2s Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum Function [CHOD_STRS0] Bifunctional enzyme that catalyzes the oxidation of the 3-beta-hydroxy group of cholesterol and the isomerization of the double bond of the resulting product. Publication Abstract from PubMed Cholesterol oxidase (CO) is a flavoenzyme that catalyzes the oxidation and isomerization of cholesterol to cholest-4-en-3-one. The reductive half reaction occurs via a hydride transfer from the substrate to the FAD cofactor. The structures of CO reduced with dithionite under aerobic conditions and in the presence of the substrate 2-propanol under both aerobic and anaerobic conditions are presented. The 1.32 A resolution structure of the dithionite-reduced enzyme reveals a sulfite molecule covalently bound to the FAD cofactor. The isoalloxazine ring system displays a bent structure relative to that of the oxidized enzyme, and alternate conformations of a triad of aromatic residues near to the cofactor are evident. A 1.12 A resolution anaerobically trapped reduced enzyme structure in the presence of 2-propanol does not show a similar bending of the flavin ring system, but does show alternate conformations of the aromatic triad. Additionally, a significant difference electron-density peak is observed within a covalent-bond distance of N5 of the flavin moiety, suggesting that a hydride-transfer event has occurred as a result of substrate oxidation trapping the flavin in the electron-rich reduced state. The hydride transfer generates a tetrahedral geometry about the flavin N5 atom. High-level density-functional theory calculations were performed to correlate the crystallographic findings with the energetics of this unusual arrangement of the flavin moiety. These calculations suggest that strong hydrogen-bond interactions between Gly120 and the flavin N5 centre may play an important role in these structural features. High-resolution structures of cholesterol oxidase in the reduced state provide insights into redox stabilization.,Golden E, Karton A, Vrielink A Acta Crystallogr D Biol Crystallogr. 2014 Dec 1;70(Pt 12):3155-66. doi:, 10.1107/S139900471402286X. Epub 2014 Nov 22. PMID:25478834 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Cholesterol oxidase

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