Abeyawardhane Dinendra L, Sevdalis Spiridon E, Adipietro Kaylin A, Godoy-Ruiz Raquel, Varney Kristen M, Nawaz Izza F, Spittel Alejandro X, Rustandi Richard R, Silin Vitalii I, des Georges Amedee, Pozharski Edwin, Weber David J
bioRxiv. 2023 Sep 21:2023.08.18.553786. doi: 10.1101/2023.08.18.553786.
The binary toxin (CDT) enters host cells via endosomal delivery like many other 'AB'-type binary toxins. In this study, the cell-binding component of CDT, termed CDTb, was found to bind and form pores in lipid bilayers upon depleting free Ca ion concentrations, and not by lowering pH, as found for other binary toxins (i.e., anthrax). Cryoelectron microscopy, nuclear magnetic resonance spectroscopy, surface plasmon resonance, electrochemical impedance spectroscopy, CDT toxicity studies, and site directed mutagenesis show that dissociation of Ca from a single site in receptor binding domain 1 (RBD1) of CDTb is consistent with a molecular mechanism in which Ca dissociation from RBD1 induces a "trigger" via conformational exchange that enables CDTb to bind and form pores in endosomal membrane bilayers as free Ca concentrations decrease during CDT endosomal delivery.
与许多其他“AB”型二元毒素一样，二元毒素（CDT）通过内体递送进入宿主细胞。在本研究中，发现CDT的细胞结合成分CDTb在耗尽游离钙离子浓度时会结合并在脂质双层中形成孔道，而不像其他二元毒素（如炭疽毒素）那样通过降低pH来形成孔道。冷冻电子显微镜、核磁共振光谱、表面等离子体共振、电化学阻抗谱、CDT毒性研究和定点诱变表明，Ca从CDTb的受体结合结构域1（RBD1）中的单个位点解离，这与一种分子机制一致，即随着CDT内体递送过程中游离Ca浓度降低，Ca从RBD1解离通过构象交换诱导“触发”，使CDTb能够在内体膜双层中结合并形成孔道。
