Oligomerization of the Clostridioides difficile transferase B component proceeds through a stepwise mechanism
Year: 2025
Type: article
Abstract: Clostridioides difficile is a gram-positive, pathogenic bacterium and is currently the leading cause of hospital-acquired, infectious diarrhea in the United States. During infection, C. difficile produces and secretes up to three toxins called Toxin A, Toxin B, and the C. difficile transferase (CDT). While Toxin A and Toxin B are thought to drive the pathology associated with the disease, strains that produce CDT have been linked to increased disease severity, higher rates of infection recurrence, and increased incidence of mortality. A basic understanding of how CDT intoxicates host cells has emerged over the past two decades and includes a framework that relies on the oligomerization of the components that comprise CDT to promote cellular intoxication. Although several key steps of this process have been biochemically described, a clear, molecular description of toxin assembly has not been resolved. We have collected cryogenic electron microscopy (Cryo-EM) data of purified, recombinant CDT. From these data, we have generated several structural snapshots of the toxin, including a series of structures that correspond to intermediates that form during oligomerization. These structures provide insight into the mechanism underlying toxin assembly and highlight a role for structural plasticity during this process. We have also shown that these partially assembled toxins are equally potent in cytotoxicity assays supporting this model in a cellular context. Finally, we show that CDTb oligomers are stabilized by CDTa and assembly is triggered by hydrophobic molecules. Author Summary Clostridioides difficile is the leading cause of hospital-acquired, infectious diarrhea in the United States. Strains of C. difficile that produce a toxin known as the C. difficile Transferase (CDT) are linked to more severe presentations of the disease in clinical settings. Despite its apparent importance, a molecular model of CDT intoxication remains undeveloped. Reported here are several Cryo-EM structures that describe the mode of CDT assembly which occurs through the stochastic and sequential addition of proteins that comprise the toxin.
Source: PLoS Pathogens
Authors: Robin M. Mullard, Michael J. Sheedlo
Institution: University of Minnesota
Language: English
Subfield: Infectious Diseases
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $3,043
Funders: Foundation for the National Institutes of Health, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, University of Minnesota, National Institutes of Health, University of California, San Francisco, National Institute of General Medical Sciences, National Institute of Allergy and Infectious Diseases, SLAC National Accelerator Laboratory
OpenAlex ID: W4412530491