Anthrax: Toxin Delivery

   Bacillus anthracis is the bacteria responsible for the disease anthrax. Anthrax has recently received a large amount of attention as a possible biological weapon. As a result of recent events, there is a renewed interest in understanding the mechanism of disease caused by Bacillus anthracis infection.

   Anthrax: Toxin Delivery highlights the steps of anthrax toxin delivery into the cell. The process begins with binding of protective antigens (PA) from Bacillus anthracis to the anthrax toxin receptor (ATR). ATR is a type-I membrane protein. Following binding of PA to ATR, PA is cleaved by a cellular protease to produce the active form of PA. In this form, PA is able to multimerize into a heptamer. As a heptamer, PA is capable of binding the edema factor (EF) and lethal factor (LF).

   Upon binding of EF and LF to the PA/ATR complex, endocytosis causing the toxins to translocate into the cell via intracellular vesicle formation. The PA heptamer inserts into the vesicle membrane following a reduction in pH, opening a pore to the cytoplasm. The EF and LF toxins translocate across the membrane where they disrupt intracellular processes by various mechanisms.