One of the three protein components of Anthrax toxin, protective antigen (PA) is the central moiety that mediates the entry of lethal factor and edema factor into the target cell. PA binds to the cell surface via a type I membrane protein with a von Willebrand factor A domain called anthrax toxin receptor. After proteolytic activation to a 63 kDa fragment, PA self-associates to form a heptameric cation-selective, voltage-gated membrane channel. Alternative Names: Bacillus Anthracis Protein, Recombinant B Anthracis , Anthrax Protein, Bacillus Anthracis Lethal Antigen Recombinant Protein