Abstract
Anthrax toxin is a major virulence factor of Bacillus anthracis, a Gram-positive bacterium which can form highly stable spores that are the causative agents of the disease, anthrax. While chiefly a disease of livestock, spores can be “weaponized” as a bio-terrorist agent, and can be deadly if not recognized and treated early with antibiotics. The intracellular pathways affected by the enzymes are broadly understood and are not discussed here. This chapter focuses on what is known about the assembly of secreted toxins on the host cell surface and how the toxin is delivered into the cytosol. The central component is the “Protective Antigen”, which self-oligomerizes and forms complexes with its pay-load, either Lethal Factor or Edema Factor. It binds a host receptor, CMG2, or a close relative, triggering receptor-mediated endocytosis, and forms a remarkably elegant yet powerful machine that delivers toxic enzymes into the cytosol, powered only by the pH gradient across the membrane. We now have atomic structures of most of the starting, intermediate and final assemblies in the infectious process. Together with a major body of biophysical, mutational and biochemical work, these studies reveal a remarkable story of both how toxin assembly is choreographed in time and space.
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Notes
- 1.
All of the complexes described here are consistent with each other and with a large body of biochemical and biophysical studies; but they bear no resemblance to earlier EM-derived models of a PA-LF complex (Ren et al. 2004; Tama et al. 2006), which cannot be rationalized in terms of any of the other published complexes, or inferred from translocation intermediates, and so remains enigmatic.
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Liddington, R.C. (2021). Assembly and Function of the Anthrax Toxin Protein Translocation Complex. In: Harris, J.R., Marles-Wright, J. (eds) Macromolecular Protein Complexes III: Structure and Function. Subcellular Biochemistry, vol 96. Springer, Cham. https://doi.org/10.1007/978-3-030-58971-4_18
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