7u1z

Crystal structure of the DRBD and CROPs of TcdA

spinqualitylabelsall models 7u1z, resolution 3.18Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 7u1z 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 3.18Å Ligands: SO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function TCDA_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). TcdA and TcdB constitute the main toxins that mediate 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 TcdB, TcdA is less virulent and less important for inducing the host inflammatory and innate immune responses (PubMed:19252482). This form constitutes the precursor of the toxin: it enters into host cells and mediates autoprocessing to release the active toxin (Glucosyltransferase TcdA) into the host cytosol (By similarity). Targets colonic epithelia by binding to some receptor, and enters host cells via clathrin-mediated endocytosis (By similarity). Binding to LDLR, as well as carbohydrates and sulfated glycosaminoglycans on host cell surface contribute to entry into cells (PubMed:1670930, PubMed:31160825, PubMed:16622409). In contrast to TcdB, Frizzled receptors FZD1, FZD2 and FZD7 do not act as host receptors in the colonic epithelium for TcdA (PubMed:27680706). 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 (By similarity). This activates the peptidase C80 domain and autocatalytic processing, releasing the N-terminal part (Glucosyltransferase TcdA), which constitutes the active part of the toxin, in the cytosol (PubMed:17334356, PubMed:19553670, PubMed:27571750).[UniProtKB:P18177] Active form of the toxin, which is released into the host cytosol following autoprocessing and inactivates small GTPases (PubMed:7775453, PubMed:24905543, PubMed:30622517, PubMed:22747490, PubMed:22267739). Acts by mediating monoglucosylation of small GTPases of the Rho family (Rac1, RhoA, RhoB, RhoC, Rap2A 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:7775453, PubMed:24905543, PubMed:30622517, PubMed:22747490, PubMed:22267739). 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:7775453). Also able to catalyze monoglucosylation of some members of the Ras family (H-Ras/HRAS, K-Ras/KRAS and N-Ras/NRAS), but with much less efficiency than with Rho proteins, suggesting that it does not act on Ras proteins in vivo (PubMed:30622517). Publication Abstract from PubMed Clostridioides difficile toxin A and B (TcdA and TcdB) are two major virulence factors responsible for diseases associated with C. difficile infection (CDI). Here, we report the 3.18-A resolution crystal structure of a TcdA fragment (residues L843-T2481), which advances our understanding of the complete structure of TcdA holotoxin. Our structural analysis, together with complementary single molecule FRET and limited proteolysis studies, reveal that TcdA adopts a dynamic structure and its CROPs domain can sample a spectrum of open and closed conformations in a pH-dependent manner. Furthermore, a small globular subdomain (SGS) and the CROPs protect the pore-forming region of TcdA in the closed state at neutral pH, which could contribute to modulating the pH-dependent pore formation of TcdA. A rationally designed TcdA mutation that trapped the CROPs in the closed conformation showed drastically reduced cytotoxicity. Taken together, these studies shed new lights into the conformational dynamics of TcdA and its roles in TcdA intoxication. Structure and conformational dynamics of Clostridioides difficile toxin A.,Chen B, Basak S, Chen P, Zhang C, Perry K, Tian S, Yu C, Dong M, Huang L, Bowen ME, Jin R Life Sci Alliance. 2022 Mar 15;5(6). pii: 5/6/e202201383. doi:, 10.26508/lsa.202201383. Print 2022 Jun. PMID:35292538 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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