National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
P41GM103832
United States
Welch Foundation
A-1863
United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
U24GM116787
United States
Citation
Journal: PLoS Biol / Year: 2019 Title: Selection and characterization of ultrahigh potency designed ankyrin repeat protein inhibitors of C. difficile toxin B. Authors: Rudo Simeon / Mengqiu Jiang / Ana M Chamoun-Emanuelli / Hua Yu / Yongrong Zhang / Ran Meng / Zeyu Peng / Joanita Jakana / Junjie Zhang / Hanping Feng / Zhilei Chen / Abstract: Clostridium difficile infection (CDI) is a major nosocomial disease associated with significant morbidity and mortality. The pathology of CDI stems primarily from the 2 C. difficile-secreted ...Clostridium difficile infection (CDI) is a major nosocomial disease associated with significant morbidity and mortality. The pathology of CDI stems primarily from the 2 C. difficile-secreted exotoxins-toxin A (TcdA) and toxin B (TcdB)-that disrupt the tight junctions between epithelial cells leading to the loss of colonic epithelial barrier function. Here, we report the engineering of a series of monomeric and dimeric designed ankyrin repeat proteins (DARPins) for the neutralization of TcdB. The best dimeric DARPin, DLD-4, inhibited TcdB with a half maximal effective concentration (EC50) of 4 pM in vitro, representing an approximately 330-fold higher potency than the Food and Drug Administration (FDA)-approved anti-TcdB monoclonal antibody bezlotoxumab in the same assay. DLD-4 also protected mice from a toxin challenge in vivo. Cryo-electron microscopy (cryo-EM) studies revealed that the 2 constituent DARPins of DLD-4-1.4E and U3-bind the central and C-terminal regions of the delivery domain of TcdB. Competitive enzyme-linked immunosorbent assay (ELISA) studies showed that the DARPins 1.4E and U3 interfere with the interaction between TcdB and its receptors chondroitin sulfate proteoglycan 4 (CSPG4) and frizzled class receptor 2 (FZD2), respectively. Our cryo-EM studies revealed a new conformation of TcdB (both apo- and DARPin-bound at pH 7.4) in which the combined repetitive oligopeptides (CROPS) domain points away from the delivery domain. This conformation of the CROPS domain is in stark contrast to that seen in the negative-stain electron microscopy (EM) structure of TcdA and TcdB at the same pH, in which the CROPS domain bends toward and "kisses" the delivery domain. The ultrapotent anti-TcdB molecules from this study serve as candidate starting points for CDI drug development and provide new biological tools for studying the pathogenicity of C. difficile. The structural insights regarding both the "native" conformation of TcdB and the putative sites of TcdB interaction with the FZD2 receptor, in particular, should help accelerate the development of next-generation anti-C. difficile toxin therapeutics.
History
Deposition
Aug 21, 2017
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Header (metadata) release
Oct 11, 2017
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Map release
Aug 29, 2018
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Update
Jan 29, 2020
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Current status
Jan 29, 2020
Processing site: RCSB / Status: Released
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