Functional Characterization of Protease-Treated Bacillus anthracis ProtectiveAntigen

摘要

Characterization of the functional domains of Bacillus anthracis protectiveantigen (PA, 83-kDa), the common cellular binding molecule for both anthrax edema toxin and anthrax lethal toxin, is important for understanding the mechanism of entry and action of the anthrax toxins. In this study, we generated both biologically active (facilitates killing of J774A.1 cells in combination with lethal factor, LF) and inactive preparations of PA by protease treatment. Limited proteolytic digestion of PA in vitro with trypsin generated a 20-kDa fragment and a biologically active 63kDa fragment. In contrast, limited digestion of PA with chymotrypsin yielded a preparation containing 37 and 47-kDa fragments defective for biological activity. Treatment with both chymotrypsin and trypsin generated three major fragments, 20, '17,' and 47 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This PA preparation was also biologically inactive.