A model of anthrax toxin lethal factor bound to protective antigen.
Anthrax toxin is made up of three proteins: the edema factor (EF), lethal factor (LF) enzymes, and the multifunctional protective antigen (PA). Proteolytically activated PA heptamerizes, binds the EF/LF enzymes, and forms a pore that allows for EF/LF passage into host cells. Using directed mutagenesis, we identified three LF-PA contact points defined by a specific disulfide crosslink and two pairs of complementary charge-reversal mutations. These contact points were consistent with the lowest energy LF-PA complex found by using Rosetta protein-protein docking. These results illustrate how biochemical and computational methods can be combined to produce reliable models of large complexes. The model shows that EF and LF bind through a highly electrostatic interface, with their flexible N-terminal region positioned at the entrance of the heptameric PA pore and thus poised to initiate translocation in an N- to C-terminal direction.
Lacy
D Borden
DB
Department of Microbiology and Molecular Genetics and Graduate Group of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
Lin
Henry C
HC
Melnyk
Roman A
RA
Schueler-Furman
Ora
O
Reither
Laura
L
Cunningham
Kristina
K
Baker
David
D
Collier
R John
RJ
D000942:Antigens, Bacterial / Q000737:chemistry* / Q000378:metabolism; D001427:Bacterial Toxins / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D055672:Static Electricity
D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D004220:Disulfides; C030325:anthrax toxin