Assembly and Function of the Anthrax Toxin Protein Translocation Complex.

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Bacillus anthracis is a Gram-positive bacterium causing anthrax, a disease of livestock and a potential bioterrorism agent.
• Anthrax toxin is a primary virulence factor, with spores being highly stable and deadly if untreated.
• While intracellular pathways are understood, the focus here is on toxin assembly and delivery.

Purpose of the Study:

• To elucidate the assembly of secreted anthrax toxins on host cell surfaces.
• To explain the mechanism of toxin delivery into the host cell cytosol.
• To integrate structural and biophysical data to understand the infectious process.

Main Methods:

• Analysis of atomic structures of toxin assembly intermediates and final complexes.
• Biophysical studies to investigate toxin assembly dynamics.
• Mutational and biochemical analyses to probe protein interactions.

Main Results:

• The protective antigen (PA) self-oligomerizes and complexes with lethal factor (LF) or edema factor (EF).
• PA binds host receptor CMG2, initiating receptor-mediated endocytosis.
• Toxin delivery into the cytosol is powered by the pH gradient across the membrane.

Conclusions:

• Atomic structures and biophysical data reveal the choreographed assembly of anthrax toxin.
• The process demonstrates an elegant and powerful mechanism for enzyme delivery.
• Understanding this process is crucial for developing targeted interventions against anthrax.