Anthrax protective antigen
Anthrax protective antigen (PA) is the cell-binding part of the Bacillus anthracis anthrax toxin. The anthrax toxin is composed of the PA, lethal factor and edema factor. The PA translocates the lethal and edema factors into the cell. The 83kD form of PA (PA83) binds to the anthrax toxin receptor. A 20kD fragment is cleaved off the PA83 and the remaining PA63 assembles into ring-shaped oligomer which becomes a membrane pre-channel. PA domain 4 is important for receptor recognition and pore formation. The PA pre-channel binds the lethal and edema factors allowing them to penetrate the membrane via pH gradient.
PA83
1acc, 3tew, 3q8a, 3q8b – PA
3tex, 3tey, 3tez, 3q8c, 3q8e – PA (mutant)
3mhz, 3q8f – PA with fluoro-histidine
1t6b – PA + anthrax toxin receptor A/I domain
PA63
3hvd – PA63 (mutant)
1tzo – PA63
1tzn – PA63 + anthrax toxin receptor VWA domain
3kwv – PA63 (mutant) + lethal factor
PA domain 4