Structure of anthrax lethal toxin prepore complex suggests a pathway for efficient cell entry.
Anthrax toxin comprises three soluble proteins: protective antigen (PA), lethal factor (LF), and edema factor (EF). PA must be cleaved by host proteases before it oligomerizes and forms a prepore, to which LF and EF bind. After endocytosis of this tripartite complex, the prepore transforms into a narrow transmembrane pore that delivers unfolded LF and EF into the host cytosol. Here, we find that translocation of multiple 90-kD LF molecules is rapid and efficient. To probe the molecular basis of this translocation, we calculated a three-dimensional map of the fully loaded (PA63)7-(LF)3 prepore complex by cryo-electron microscopy (cryo-EM). The map shows three LFs bound in a similar way to one another, via their N-terminal domains, to the surface of the PA heptamer. The model also reveals contacts between the N- and C-terminal domains of adjacent LF molecules. We propose that this molecular arrangement plays an important role in the maintenance of translocation efficiency through the narrow PA pore.
Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada.
Lucien
L
Fabre
Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037.
Eugenio
E
Santelli
Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada.
Driss
D
Mountassif
Departments of Physics, Université de Montréal, Montréal, Québec H3T 1J4, Canada Department of Physiology, Université de Montréal, Montréal, Québec H3T 1J4, Canada Groupe d'Étude des Protéines Membranaires (GÉPROM), Université de Montréal, Montréal, Québec H3T 1J4, Canada.
Annemarie
A
Donoghue
Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada.
Aviroop
0000-0002-0393-6280
A
Biswas
Departments of Physics, Université de Montréal, Montréal, Québec H3T 1J4, Canada Department of Physiology, Université de Montréal, Montréal, Québec H3T 1J4, Canada Groupe d'Étude des Protéines Membranaires (GÉPROM), Université de Montréal, Montréal, Québec H3T 1J4, Canada.
Rikard
0000-0003-4484-2907
R
Blunck
Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037.
Dorit
D
Hanein
Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037.
Niels
N
Volkmann
Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037 isabelle.rouiller@mcgill.ca rlidding@sbpdiscovery.org.
Robert
R
Liddington
Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada isabelle.rouiller@mcgill.ca rlidding@sbpdiscovery.org.
Isabelle
I
Rouiller
D000942:Antigens, Bacterial / Q000737:chemistry*; D001427:Bacterial Toxins / Q000737:chemistry*; D001692:Biological Transport; D004926:Escherichia coli; D008958:Models, Molecular; D011487:Protein Conformation; D017510:Protein Folding; D013329:Structure-Activity Relationship
D000942:Antigens, Bacterial; D001427:Bacterial Toxins; C030325:anthrax toxin
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