10oi

Structure of Clostridium difficile Toxin B (TcdB) glucosyltransferase in complex with UDP linked isofagomine analog 3-5

spinqualitylabelsall models 10oi, resolution 2.65Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 10oi is a 2 chain structure with sequence from Clostridioides difficile. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.65Å Ligands: A1C96, GOL, MN, UDP Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function TCDB_CLODI Precursor of a cytotoxin that targets and disrupts the colonic epithelium, inducing the host inflammatory and innate immune responses and resulting in diarrhea and pseudomembranous colitis (PubMed:20844489, PubMed:24919149). TcdB constitutes the main toxin that mediates the pathology of C.difficile infection, an opportunistic pathogen that colonizes the colon when the normal gut microbiome is disrupted (PubMed:19252482, PubMed:20844489). Compared to TcdA, TcdB is more virulent and more important for inducing the host inflammatory and innate immune responses (PubMed:19252482, PubMed:24919149). This form constitutes the precursor of the toxin: it enters into host cells and mediates autoprocessing to release the active toxin (Glucosyltransferase TcdB) into the host cytosol (PubMed:10768933, PubMed:11152463, PubMed:12941936, PubMed:17334356, PubMed:20498856). Targets colonic epithelia by binding to the frizzled receptors FZD1, FZD2 and FZD7, and enters host cells via clathrin-mediated endocytosis (PubMed:27680706). Frizzled receptors constitute the major host receptors in the colonic epithelium, but other receptors, such as CSPG4 or NECTIN3/PVRL3, have been identified (PubMed:25547119, PubMed:26038560, PubMed:27680706). Binding to carbohydrates and sulfated glycosaminoglycans on host cell surface also contribute to entry into cells (By similarity). Once entered into host cells, acidification in the endosome promotes the membrane insertion of the translocation region and formation of a pore, leading to translocation of the GT44 and peptidase C80 domains across the endosomal membrane (PubMed:11152463, PubMed:12941936, PubMed:24567384). This activates the peptidase C80 domain and autocatalytic processing, releasing the N-terminal part (Glucosyltransferase TcdB), which constitutes the active part of the toxin, in the cytosol (PubMed:17334356, PubMed:27571750).[UniProtKB:P16154] Active form of the toxin, which is released into the host cytosol following autoprocessing and inactivates small GTPases (PubMed:16157585, PubMed:17901056, PubMed:24905543, PubMed:24919149, PubMed:7777059, PubMed:8144660). Acts by mediating monoglucosylation of small GTPases of the Rho family (Rac1, RhoA, RhoB, RhoC, RhoG and Cdc42) in host cells at the conserved threonine residue located in the switch I region ('Thr-37/35'), using UDP-alpha-D-glucose as the sugar donor (PubMed:16157585, PubMed:17901056, PubMed:24905543, PubMed:24919149, PubMed:7777059). Monoglucosylation of host small GTPases completely prevents the recognition of the downstream effector, blocking the GTPases in their inactive form, leading to actin cytoskeleton disruption and cell death, resulting in the loss of colonic epithelial barrier function (PubMed:24919149, PubMed:7777059). Publication Abstract from PubMed Clostridioides difficile (C. difficile) is the leading cause of hospital-acquired life-threatening diarrhea. C. difficile toxins TcdA and TcdB contain a glucosyltransferase domain (GTD) that glucosylates and inactivates host GTPases, disrupting the actin cytoskeleton and compromising epithelial integrity. TcdB, the most potent virulence factor, drives disease progression and is a high-priority target forC. difficiletreatment and prevention. The iminosugar isofagomine has been shown to inhibit the GTD activity of TcdB by an uncompetitive inhibition mechanism, but requires the uridine 5'-diphosphate (UDP) reaction product. Compound classes synthesized here, ranging from isofagomine analogues to acyclic mimics, probe which modifications can tap into UDP-binding energy to enhance inhibition. Structure-activity relationship studies of isofagomine derivatives demonstrate remarkable specificity for isofagomine and limited advantage in accessing the UDP-binding site. Fluorescence and absorbance assays allowed facile inhibition assessment of TcdB's UDP-glucose hydrolysis. The molecules reported here guide scaffolds for future catalytic site inhibitors. Isofagomine Derivatives as TcdB Glucosyltransferase Inhibitors.,Shaffer KJ, Gilaj N, Wagner AG, Popadynec M, Groom DP, Hughes LA, Ghosh A, Paparella A, Tyler PC, Lamiable-Oulaidi F, Schramm VL J Med Chem. 2026 Jul 1. doi: 10.1021/acs.jmedchem.6c00369. PMID:42383693 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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