1.C.42.1.1
Bacillus anthracis protective antigen (PA). Many cationic compounds inhibit in nM - mM concentration ranges (Yamini et al. 2016). Both symmetry and size of cyclodextrin inhibitors and the toxin pore are important for effective inhibition (Yannakopoulou et al., 2011).  A cryo electron microscopic structure of the anthrax protective antigen translocon and the N-terminal domain of anthrax lethal factor (aLF) inserted into a nanodisc model lipid bilayer has been solved revealing a cap, a narrow stalk and a transmembrane channel (Gogol et al. 2013).  Poly(amindo)amine (PAMAM) dentrimers block activity (Förstner et al. 2014).  The 3-d structure of PA, showing the channel and the φ-clamp, and providing information about the multi-step mechanism by which low pH is sensed and the membrane-spanning channel is formed has been published (Jiang et al. 2015).  The export of the lethal factor and edema factor from the endosome into the host cytosol is dependent on the proton motive force (pmf) (Krantz et al. 2006; Colby and Krantz 2015). Translocation of anthrax toxin's lethal factor is initiated by entry of its N terminus into the protective antigen channel (Zhang et al. 2004). The endopeptidase activity of anthrax lethal factor (aLF) prevents the destruction of B.anthracis spores intracellularly by host macrophages, meanwhile disabling the signaling pathways extracellularly that leads to host lethality. This activity has been used for nanopore detection (Li et al. 2022).