Edema Factor of Bacillus Anthracis Interacting with Its Inhibitors

Edema factor (EF), a toxin of Bacillus anthracis, is activated by calmodulin (CaM). The EF/CAM interaction induces the appearance of a site catalyzing the production of cyclic AMP (cAMP), through the folding of a disordered switch. Previous studies (Laine, 2010) have shown that thiophen ureidoacids inhibit the cAMP production, but their binding site is not precisely known. These inhibitors were discovered by targeting in silico the switch, and, interestingly, similar compounds were shown to target the switch region of bacterial RNAP (Sahner, 2013; Fruth, 2014). Beside, interactions between adefovir compound and EF have been extensively studied (Shen, 2004; Česnek, 2018). An X-ray crystallographic structure of the EF/adefovir complex displays the compound bound into the catalytic site in the presence of a Rubidium ion. The disordered switch observed in the inactive EF and the partial knowledge of the interactions between the protein and these inhibitors open a wide range of possibilities for the interactions. In the present work, we use various experimental approaches, biochemical assays and NMR, as well as molecular modeling to investigate these interactions. Česnek et al. Analogues as Potent and Selective Inhibitors of Adenylate Cyclases from Bordetella pertussis and Bacillus anthracis. ChemMedChem 2018. Fruth et al. Binding mode characterization of novel RNA polymerase inhibitors using a combined biochemical and NMR approach. ACS Chem Biol 2014. Laine et al. Use of allostery to identify inhibitors of calmodulin induced activation of Bacillus anthracis edema factor. Proc Natl Acad Sci USA 2010. Sahner et al. Novel small molecule inhibitors targeting the “switch region” of bacterial RNAP: structure-based optimization of a virtual screening hit. Eur J Med Chem 2013. Shen et al. Selective inhibition of anthrax edema factor by adefovir, a drug for chronic hepatitis B virus infection.Proc Natl Acad Sci USA 2004.