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Specificity
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Recognizes the Protective Antigen of the anthrax toxin. Bacillus anthracis produces a toxin composed of three proteins, the Protective Antigen (PA), the Edema Factor (EF) and the Lethal Factor (LF). The three proteins depend on each other for their toxic effect. Both EF and LF functions intracellularly but are too large to enter the cell through existing channels. The PA is responsible for transporting the EF and LF into cells. The 83kD PA (PA83) binds to the cell surface where a 20 kD N-terminal fragment (PA20) is cleaved off, exposing binding sites for LF and EF. The remaining 63 kD portion (PA63) oligomerizes to form a heptamer pre-pore, which then associates with up to three molecules of EF and/or LF. The receptor complex is internalized within endocytotic vessels that are subsequently acidified, transforming the PA heptamer into a pore that releases the active enzymes EF (an adenylate cyclase) and LF (a protease targeting MAPKKs) into the cytosol. Does not cross-react with the Lethal Factor of Bacillus anthracis, Yersinia pestis, Francisella tularensis or Toxoplasma gondii. Recognizes both the 83kD and 63kD truncated form of PA.
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