1
|
Cryo-EM structure of the fully-loaded asymmetric anthrax lethal toxin in its heptameric pre-pore state. PLoS Pathog 2020; 16:e1008530. [PMID: 32810181 PMCID: PMC7462287 DOI: 10.1371/journal.ppat.1008530] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 09/01/2020] [Accepted: 06/27/2020] [Indexed: 12/20/2022] Open
Abstract
Anthrax toxin is the major virulence factor secreted by Bacillus anthracis, causing high mortality in humans and other mammals. It consists of a membrane translocase, known as protective antigen (PA), that catalyzes the unfolding of its cytotoxic substrates lethal factor (LF) and edema factor (EF), followed by translocation into the host cell. Substrate recruitment to the heptameric PA pre-pore and subsequent translocation, however, are not well understood. Here, we report three high-resolution cryo-EM structures of the fully-loaded anthrax lethal toxin in its heptameric pre-pore state, which differ in the position and conformation of LFs. The structures reveal that three LFs interact with the heptameric PA and upon binding change their conformation to form a continuous chain of head-to-tail interactions. As a result of the underlying symmetry mismatch, one LF binding site in PA remains unoccupied. Whereas one LF directly interacts with a part of PA called α-clamp, the others do not interact with this region, indicating an intermediate state between toxin assembly and translocation. Interestingly, the interaction of the N-terminal domain with the α-clamp correlates with a higher flexibility in the C-terminal domain of the protein. Based on our data, we propose a model for toxin assembly, in which the relative position of the N-terminal α-helices in the three LFs determines which factor is translocated first.
Collapse
|
2
|
Fabre L, Santelli E, Mountassif D, Donoghue A, Biswas A, Blunck R, Hanein D, Volkmann N, Liddington R, Rouiller I. Structure of anthrax lethal toxin prepore complex suggests a pathway for efficient cell entry. J Gen Physiol 2017; 148:313-24. [PMID: 27670897 PMCID: PMC5037343 DOI: 10.1085/jgp.201611617] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 08/25/2016] [Indexed: 01/20/2023] Open
Abstract
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.
Collapse
Affiliation(s)
- Lucien Fabre
- 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
| | - Eugenio Santelli
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Driss Mountassif
- 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
| | - Annemarie Donoghue
- 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
| | - Aviroop Biswas
- 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
| | - Rikard Blunck
- 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
| | - Dorit Hanein
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Niels Volkmann
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Robert Liddington
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Isabelle Rouiller
- 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
| |
Collapse
|
3
|
The Molecular Basis of Toxins' Interactions with Intracellular Signaling via Discrete Portals. Toxins (Basel) 2017; 9:toxins9030107. [PMID: 28300784 PMCID: PMC5371862 DOI: 10.3390/toxins9030107] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 03/02/2017] [Accepted: 03/04/2017] [Indexed: 12/20/2022] Open
Abstract
An understanding of the molecular mechanisms by which microbial, plant or animal-secreted toxins exert their action provides the most important element for assessment of human health risks and opens new insights into therapies addressing a plethora of pathologies, ranging from neurological disorders to cancer, using toxinomimetic agents. Recently, molecular and cellular biology dissecting tools have provided a wealth of information on the action of these diverse toxins, yet, an integrated framework to explain their selective toxicity is still lacking. In this review, specific examples of different toxins are emphasized to illustrate the fundamental mechanisms of toxicity at different biochemical, molecular and cellular- levels with particular consideration for the nervous system. The target of primary action has been highlighted and operationally classified into 13 sub-categories. Selected examples of toxins were assigned to each target category, denominated as portal, and the modulation of the different portal’s signaling was featured. The first portal encompasses the plasma membrane lipid domains, which give rise to pores when challenged for example with pardaxin, a fish toxin, or is subject to degradation when enzymes of lipid metabolism such as phospholipases A2 (PLA2) or phospholipase C (PLC) act upon it. Several major portals consist of ion channels, pumps, transporters and ligand gated ionotropic receptors which many toxins act on, disturbing the intracellular ion homeostasis. Another group of portals consists of G-protein-coupled and tyrosine kinase receptors that, upon interaction with discrete toxins, alter second messengers towards pathological levels. Lastly, subcellular organelles such as mitochondria, nucleus, protein- and RNA-synthesis machineries, cytoskeletal networks and exocytic vesicles are also portals targeted and deregulated by other diverse group of toxins. A fundamental concept can be drawn from these seemingly different toxins with respect to the site of action and the secondary messengers and signaling cascades they trigger in the host. While the interaction with the initial portal is largely determined by the chemical nature of the toxin, once inside the cell, several ubiquitous second messengers and protein kinases/ phosphatases pathways are impaired, to attain toxicity. Therefore, toxins represent one of the most promising natural molecules for developing novel therapeutics that selectively target the major cellular portals involved in human physiology and diseases.
Collapse
|
4
|
Power BH, Smith N, Downer B, Alisaraie L. Insight into the mechanism of chemical modification of antibacterial agents by antibiotic resistance enzymeO-phosphotransferase-IIIA. Chem Biol Drug Des 2016; 89:84-97. [DOI: 10.1111/cbdd.12835] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 07/22/2016] [Accepted: 07/25/2016] [Indexed: 11/30/2022]
Affiliation(s)
- Blake Hollett Power
- School of Pharmacy; Memorial University of Newfoundland; St. John's Newfoundland Canada
| | - Nathan Smith
- School of Pharmacy; Memorial University of Newfoundland; St. John's Newfoundland Canada
| | - Brandon Downer
- School of Pharmacy; Memorial University of Newfoundland; St. John's Newfoundland Canada
| | - Laleh Alisaraie
- School of Pharmacy; Memorial University of Newfoundland; St. John's Newfoundland Canada
- Department of Chemistry; Memorial University of Newfoundland; St. John's Newfoundland Canada
| |
Collapse
|