4np4

Clostridium difficile toxin B CROP domain in complex with FAB domains of neutralizing antibody bezlotoxumab

spinqualitylabelsall models 4np4, resolution 2.89Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4np4 is a 5 chain structure with sequence from Homo sapiens and Peptoclostridium difficile. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Resources: FirstGlance, OCA, RCSB, PDBsum Function [TOXB_CLODI] Cytotoxin. Publication Abstract from PubMed The symptoms of C. difficile infections (CDI1) are caused by two exotoxins, TcdA and TcdB, which target host colonocytes by binding to unknown cell-surface receptors, at least in part via their combined repetitive oligopeptide (CROP) domains. A combination of the anti-TcdA antibody actoxumab and the anti-TcdB antibody bezlotoxumab is currently under development for the prevention of recurrent CDI. We demonstrate here through various biophysical approaches that bezlotoxumab binds to specific regions within the N-terminal half of the TcdB CROP domain. Based on this information, we solved the X-ray structure of the N-terminal half of the TcdB CROP domain bound to Fab fragments of bezlotoxumab. The structure reveals that the TcdB CROP domain adopts a beta-solenoid fold consisting of long- and short-repeats (LR and SR), and that bezlotoxumab binds to two homologous sites within the CROP domain, partially occluding two of the four putative carbohydrate binding pockets located in TcdB. We also show that bezlotoxumab neutralizes TcdB by blocking binding of TcdB to mammalian cells. Overall, our data are consistent with a model wherein a single molecule of bezlotoxumab neutralizes TcdB by binding via its two Fab regions to two epitopes within the N-terminal half of the TcdB CROP domain, partially blocking the carbohydrate binding pockets of the toxin and blocking toxin binding to host cells. Mechanism of action and epitopes of the Clostridium difficile toxin B neutralizing antibody bezlotoxumab revealed by x-ray crystallography.,Orth P, Xiao L, Hernandez LD, Reichert P, Sheth P, Beaumont M, Yang X, Murgolo N, Ermakov G, DiNunzio E, Racine F, Karczewski J, Secore S, Ingram RN, Mayhood T, Strickland C, Therien AG J Biol Chem. 2014 May 12. pii: jbc.M114.560748. PMID:24821719 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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