title: Monitoring the kinetics of the pH-driven transition of the anthrax toxin prepore to the pore by biolayer interferometry and surface plasmon resonance.
abstract: Domain 2 of the anthrax protective antigen (PA) prepore heptamer unfolds and refolds during endosome acidification to generate an extended 100 Å β barrel pore that inserts into the endosomal membrane. The PA pore facilitates the pH-dependent unfolding and translocation of bound toxin enzymic components, lethal factor (LF) and/or edema factor, from the endosome to the cytoplasm. We constructed immobilized complexes of the prepore with the PA-binding domain of LF (LFN) to monitor the real-time prepore to pore kinetic transition using surface plasmon resonance and biolayer interferometry (BLI). The kinetics of this transition increased as the solution pH was decreased from 7.5 to 5.0, mirroring acidification of the endosome. Once it had undergone the transition, the LFN-PA pore complex was removed from the BLI biosensor tip and deposited onto electron microscopy grids, where PA pore formation was confirmed by negative stain electron microscopy. When the soluble receptor domain (ANTRX2/CMG2) binds the immobilized PA prepore, the transition to the pore state was observed only after the pH was lowered to early (pH 5.5) or late (pH 5.0) endosomal pH conditions. Once the pore formed, the soluble receptor readily dissociated from the PA pore. Separate binding experiments with immobilized PA pores and the soluble receptor indicate that the receptor has a weakened propensity to bind to the transitioned pore. This immobilized anthrax toxin platform can be used to identify or validate potential antimicrobial lead compounds capable of regulating and/or inhibiting anthrax toxin complex formation or pore transitions.
authors: Department of Biochemistry and Molecular Biology, University of Kansas Medical Center , Kansas City, Kansas 66160, United States.
authors: Subhashchandra
authors: S
authors: Naik
authors: Susan
authors: S
authors: Brock
authors: Narahari
authors: N
authors: Akkaladevi
authors: Jon
authors: J
authors: Tally
authors: Wesley
authors: W
authors: McGinn-Straub
authors: Na
authors: N
authors: Zhang
authors: Phillip
authors: P
authors: Gao
authors: E P
authors: EP
authors: Gogol
authors: B L
authors: BL
authors: Pentelute
authors: R John
authors: RJ
authors: Collier
authors: Mark T
authors: MT
authors: Fisher
mesh_terms: D000942:Antigens, Bacterial / Q000737:chemistry* / Q000648:ultrastructure; D001427:Bacterial Toxins / Q000737:chemistry*; D015374:Biosensing Techniques; D011992:Endosomes / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D055767:Immobilized Proteins / Q000737:chemistry*; D007368:Interferometry; D007425:Intracellular Membranes / Q000378:metabolism*; D007700:Kinetics; D008823:Micelles; D008854:Microscopy, Electron; D017510:Protein Folding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D018000:Receptors, Peptide / Q000378:metabolism; D020349:Surface Plasmon Resonance
chemical_list: C447150:ANTXR2 protein, human; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D055767:Immobilized Proteins; D008823:Micelles; D018000:Receptors, Peptide; C030325:anthrax toxin
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