Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA.
Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA.
Nat Struct Mol Biol. 2019 Aug;26(8):712-719. doi: 10.1038/s41594-019-0268-0. Epub 2019 Jul 15.
Clostridium difficile is an opportunistic pathogen that establishes in the colon when the gut microbiota are disrupted by antibiotics or disease. C. difficile infection (CDI) is largely caused by two virulence factors, TcdA and TcdB. Here, we report a 3.87-Å-resolution crystal structure of TcdB holotoxin that captures a unique conformation of TcdB at endosomal pH. Complementary biophysical studies suggest that the C-terminal combined repetitive oligopeptides (CROPs) domain of TcdB is dynamic and can sample open and closed conformations that may facilitate modulation of TcdB activity in response to environmental and cellular cues during intoxication. Furthermore, we report three crystal structures of TcdB-antibody complexes that reveal how antibodies could specifically inhibit the activities of individual TcdB domains. Our studies provide novel insight into the structure and function of TcdB holotoxin and identify intrinsic vulnerabilities that could be exploited to develop new therapeutics and vaccines for the treatment of CDI.
艰难梭菌是一种机会致病菌，当肠道微生物群被抗生素或疾病破坏时，它会在结肠中定植。艰难梭菌感染（CDI）主要由两种毒力因子 TcdA 和 TcdB 引起。在这里，我们报告了 TcdB 全毒素的 3.87 Å 分辨率晶体结构，该结构捕获了内体 pH 下 TcdB 的独特构象。互补的生物物理研究表明，TcdB 的 C 末端组合重复寡肽（CROPs）结构域是动态的，可以采用开放和闭合构象，这可能有助于在中毒过程中根据环境和细胞信号来调节 TcdB 的活性。此外，我们报告了三种 TcdB-抗体复合物的晶体结构，这些结构揭示了抗体如何特异性抑制单个 TcdB 结构域的活性。我们的研究为 TcdB 全毒素的结构和功能提供了新的见解，并确定了内在的脆弱性，这些脆弱性可被利用来开发新的治疗方法和疫苗，以治疗 CDI。
