Solution Structures of Bacillus Anthracis Protective Antigen Proteins using Small Angle Neutron Scattering and Protective Antigen 63 Ion Channel Formation Kinetics

Published

December 11, 2021

Author(s)

Ariel Michelman-Ribeiro, Kenneth A. Rubinson, Vitalii Silin, John J. Kasianowicz

Abstract

We are studying the structures of bacterial toxins that form ion channels and catalyze macromolecule transport across membranes. For example, the crystal structure of the Staphylococcus aureus α-hemolysin (α-HL) channel in its functional state was confirmed using neutron reflectometry (NR) with the protein reconstituted in membranes tethered to a solid support. This method, which provides high-resolution structural information, could test putative structures of the Bacillus anthracis Protective Antigen 63 (PA63) channel, locate where B. anthracis Lethal Factor and Edema Factor toxins (LF and EF, respectively) bind to it, and determine how small molecules can inhibit the interaction of LF and EF with the channel. We report here the solution structures of PA63 and its precursor PA83 obtained with small angle neutron scattering. At near neutral pH, PA83 is a monomer and PA63 a heptamer. The latter is compared to two markedly different cryo-electron microscopy structures. We also show that although the α-HL and PA63 channels have similar gross structural features, PA63 channel formation in lipid bilayer membranes occurs at a lower rate than does α-HL and ceases within minutes. The latter phenomenon currently precludes the use of NR for elucidating the interactions between PA63, LF, EF, and putative therapeutic agents.

Citation

Toxins

Volume

13

Issue

12

Pub Type

Journals

Keywords

alpha-hemolysin, anthrax, Bacillus anthracis, β-barrel, ion channel, pore forming toxin, PA63, PA83

Citation

Michelman-Ribeiro, A. , Rubinson, K. , Silin, V. and Kasianowicz, J. (2021), Solution Structures of Bacillus Anthracis Protective Antigen Proteins using Small Angle Neutron Scattering and Protective Antigen 63 Ion Channel Formation Kinetics, Toxins (Accessed February 10, 2025)