biostudies-literatureGonti SNCRR NIH HHSNational Institute of General Medical SciencesNIGMS NIH HHS643-647https://www.ebi.ac.uk/biostudies/studies/S-EPMC8991541biostudies-literatureUnknown60(9)The anthrax toxin protective antigen (PA), the membrane binding and pore-forming component of the anthrax toxin, was studied using ¹⁹F NMR. We site-specifically labeled PA with <i>p</i>-fluorophenylalanine (pF-Phe) at Phe427, a critically important residue that comprises the ϕ-clamp that is required for translocation of edema factor (EF) and lethal factor (LF) into the host cell cytosol. We utilized ¹⁹F NMR to follow low-pH-induced structural changes in the prepore, alone and bound to the N-terminal PA binding domain of LF, LF_N. Our studies indicate that pF-Phe427 is dynamic in the prepore state and then becomes more dynamic in the transition to the pore. An increase in dynamic behavior at the ϕ-clamp may provide the necessary room for movement needed in trBiochemistrySite-Specific Labeling and ¹⁹F NMR Provide Direct Evidence for Dynamic Behavior of the Anthrax Toxin Pore ϕ-Clamp Structure.PMC8991541P20 GM103418S10 RR029220S10 RR023438S10 RR025062S10 RR008438P41 GM103399S10 RR002781P41 RR002301P20 RR017708Westler WMGonti SMiyagi MBann JGfalseSite-Specific Labeling and ¹⁹F NMR Provide Direct Evidence for Dynamic Behavior of the Anthrax Toxin Pore ϕ-Clamp Structure.The anthrax toxin protective antigen (PA), the membrane binding and pore-forming component of the anthrax toxin, was studied using ¹⁹F NMR. We site-specifically labeled PA with <i>p</i>-fluorophenylalanine (pF-Phe) at Phe427, a critically important residue that comprises the ϕ-clamp that is required for translocation of edema factor (EF) and lethal factor (LF) into the host cell cytosol. We utilized ¹⁹F NMR to follow low-pH-induced structural changes in the prepore, alone and bound to the N-terminal PA binding domain of LF, LF_N. Our studies indicate that pF-Phe427 is dynamic in the prepore state and then becomes more dynamic in the transition to the pore. An increase in dynamic behavior at the ϕ-clamp may provide the necessary room for movement needed in tr2021-01-01T00:00:00Z2021 Mar2026-05-31T06:03:18.064Z2025-02-19T01:55:25.235ZS-EPMC89915413342837910.1021/acs.biochem.0c00833