Protective antigen (PA) is the receptor binding component of anthrax toxin. The original 83 kDa protein is cleaved by cellular furin-like proteases to form an activated 63 kDa monomer, PA63. In this form, PA63 binds to other PA63 molecules forming a ring-shaped heptamer. PA63 also has binding sites specific for the enzymes LF and EF adjacent to the pore formed on the cell surface for translocation. PA should be used in approximately seven-fold excess along with either EF or LF to intoxicate cells.
List Labs provides PA in three different sizes, Product #171 is the uncleaved 83 kDa protein, Product #s 174 and 175 are PA63, which has been activated and purified, and PA63 conjugated to FITC, respectively. Additionally we provide the approximately 20 kDA fragment cleaved from PA, PA20, Product #177