21cg

Crystal structure of sulX in complex with FMN and sulfanilamide

spinqualitylabelsall models 21cg, resolution 2.83Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 21cg is a 1 chain structure with sequence from Unclassified Microbacterium. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.83Å Ligands: FMN, SAN, ZN Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function A0A482P9Z9_9MICO Publication Abstract from PubMed The sulfonamide-degrading monooxygenase sulX plays a dual role in bioremediation and antibiotic resistance, yet its molecular mechanism remains elusive. Here we report crystal structures of sulX in its ligand-free form, as an FMN-bound binary complex, and as ternary complexes with six distinct sulfonamides at resolutions ranging from 2.09 to 3.03 A. These structures reveal that sulfonamides bind on the re face of the flavin isoalloxazine ring, with their conserved 4-aminophenol and sulfonyl moieties tightly anchored by pi-stacking and hydrogen-bonding interactions, while the divergent aminated substituents extend into an open cleft with minimal specific contacts-a feature that explains the enzyme's remarkable capacity to accommodate diverse sulfonamide substrates. By integrating structural and biochemical data, we propose a catalytic mechanism involving F265-mediated substrate gating and H397-facilitated proton transfer. In addition, structure-based engineering yielded enhanced variants: A399S, which introduces new hydrogen bonds, showed a 37% increase in activity, and P422K achieved a 29% improvement. Our findings establish the structural basis of sulX-mediated sulfonamide degradation and provide a foundation for understanding sulfonamide resistance mechanisms. Structural insights into sulfonamide degradation by a two-component flavin-dependent monooxygenase.,Hu Y, Liu W, Zhang Q, Gao Z, Zhang H, Li H, Dai L J Hazard Mater. 2026 Sep 15;517:143643. doi: 10.1016/j.jhazmat.2026.143643. PMID:42748825 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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