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Krantz BA. Anthrax Toxin: Model System for Studying Protein Translocation. J Mol Biol 2024; 436:168521. [PMID: 38458604 DOI: 10.1016/j.jmb.2024.168521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 02/08/2024] [Accepted: 03/04/2024] [Indexed: 03/10/2024]
Abstract
Dedicated translocase channels are nanomachines that often, but not always, unfold and translocate proteins through narrow pores across the membrane. Generally, these molecular machines utilize external sources of free energy to drive these reactions, since folded proteins are thermodynamically stable, and once unfolded they contain immense diffusive configurational entropy. To catalyze unfolding and translocate the unfolded state at appreciable timescales, translocase channels often utilize analogous peptide-clamp active sites. Here we describe how anthrax toxin has been used as a biophysical model system to study protein translocation. The tripartite bacterial toxin is composed of an oligomeric translocase channel, protective antigen (PA), and two enzymes, edema factor (EF) and lethal factor (LF), which are translocated by PA into mammalian host cells. Unfolding and translocation are powered by the endosomal proton gradient and are catalyzed by three peptide-clamp sites in the PA channel: the α clamp, the ϕ clamp, and the charge clamp. These clamp sites interact nonspecifically with the chemically complex translocating chain, serve to minimize unfolded state configurational entropy, and work cooperatively to promote translocation. Two models of proton gradient driven translocation have been proposed: (i) an extended-chain Brownian ratchet mechanism and (ii) a proton-driven helix-compression mechanism. These models are not mutually exclusive; instead the extended-chain Brownian ratchet likely operates on β-sheet sequences and the helix-compression mechanism likely operates on α-helical sequences. Finally, we compare and contrast anthrax toxin with other related and unrelated translocase channels.
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Affiliation(s)
- Bryan A Krantz
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, 650 W. Baltimore Street, Baltimore, MD 21201, USA.
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Ma Y, Li X, Zhao R, Wu E, Du Q, Guo J, Wang L, Zhang F. Creating de novo peptide-based bioactivities: from assembly to origami. RSC Adv 2022; 12:25955-25961. [PMID: 36199601 PMCID: PMC9465703 DOI: 10.1039/d2ra03135c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 08/24/2022] [Indexed: 11/21/2022] Open
Abstract
DNA origami has created complex structures of various spatial dimensions. However, their versatility in terms of function is limited due to the lower number of the intrinsic building blocks, i.e. nucleotides, compared with the number of amino acids. Therefore, protein origami has been proposed and demonstrated to precisely fabricate artificial functional nanostructures. Despite their hierarchical folded structures, chain-like peptides and DNA share obvious similarities in both structures and properties, especially in terms of chain hybridization; therefore, replacing DNA with peptides to create bioactivities not only has high theoretical feasibility but also provides a new bottom-up synthetic strategy. However, designing functionalities with tens to hundreds of peptide chains using the similar principle of DNA origami has not been reported, although the origami strategy holds great potential to generate more complex bioactivities. In this perspective review, we have reviewed the recent progress in and highlighted the advantages of peptide assembly and origami on the orientation of artificially created bioactivities. With the great potential of peptide origami, we appeal to develop user-friendly softwares in combination with artificial intelligence.
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Affiliation(s)
- Yuxing Ma
- Wenzhou Institute, University of Chinese Academy of Sciences Wenzhou 325001 China
- Oujiang Laboratory Wenzhou Zhejiang 325000 P. R. China
- Inner Mongolia Key Laboratory of Tick-Borne Zoonotic Infectious Disease, Department of Medicine, Hetao College Bayannur 015000 China
| | - Xiaofang Li
- Wenzhou Institute, University of Chinese Academy of Sciences Wenzhou 325001 China
- Oujiang Laboratory Wenzhou Zhejiang 325000 P. R. China
- Key Laboratory of Optical Technology and Instrument for Medicine, Ministry of Education, University of Shanghai for Science and Technology Shanghai 200093 P. R. China
| | - Ruoyang Zhao
- Wenzhou Institute, University of Chinese Academy of Sciences Wenzhou 325001 China
- Oujiang Laboratory Wenzhou Zhejiang 325000 P. R. China
| | - Enqi Wu
- Inner Mongolia Key Laboratory of Tick-Borne Zoonotic Infectious Disease, Department of Medicine, Hetao College Bayannur 015000 China
| | - Qiqige Du
- Wenzhou Institute, University of Chinese Academy of Sciences Wenzhou 325001 China
- Oujiang Laboratory Wenzhou Zhejiang 325000 P. R. China
| | - Jun Guo
- Key Laboratory of Optical Technology and Instrument for Medicine, Ministry of Education, University of Shanghai for Science and Technology Shanghai 200093 P. R. China
- State Key Laboratory of Respiratory Disease, Guangzhou Institute of Oral Disease, Stomatology Hospital, School of Biomedical Engineering, Guangzhou Medical University Guangzhou 511436 China
| | - Liping Wang
- Wenzhou Institute, University of Chinese Academy of Sciences Wenzhou 325001 China
- Oujiang Laboratory Wenzhou Zhejiang 325000 P. R. China
| | - Feng Zhang
- Wenzhou Institute, University of Chinese Academy of Sciences Wenzhou 325001 China
- Oujiang Laboratory Wenzhou Zhejiang 325000 P. R. China
- Key Laboratory of Optical Technology and Instrument for Medicine, Ministry of Education, University of Shanghai for Science and Technology Shanghai 200093 P. R. China
- State Key Laboratory of Respiratory Disease, Guangzhou Institute of Oral Disease, Stomatology Hospital, School of Biomedical Engineering, Guangzhou Medical University Guangzhou 511436 China
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Liu W, Nestorovich EM. Anthrax toxin channel: What we know based on over 30 years of research. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183715. [PMID: 34332985 DOI: 10.1016/j.bbamem.2021.183715] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 07/21/2021] [Accepted: 07/24/2021] [Indexed: 10/20/2022]
Abstract
Protective antigen channel is the central component of the deadly anthrax exotoxin responsible for binding and delivery of the toxin's enzymatic lethal and edema factor components into the cytosol. The channel, which is more than three times longer than the lipid bilayer membrane thickness and has a 6-Å limiting diameter, is believed to provide a sophisticated unfoldase and translocase machinery for the foreign protein transport into the host cell cytosol. The tripartite toxin can be reengineered, one component at a time or collectively, to adapt it for the targeted cancer therapeutic treatments. In this review, we focus on the biophysical studies of the protective antigen channel-forming activity, small ion transport properties, enzymatic factor translocation, and blockage comparing it with the related clostridial binary toxin channels. We address issues linked to the anthrax toxin channel structural dynamics and lipid dependence, which are yet to become generally recognized as parts of the toxin translocation machinery.
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Affiliation(s)
- Wenxing Liu
- Department of Biology, The Catholic University of America, 620 Michigan Ave, Washington, DC 20064, USA
| | - Ekaterina M Nestorovich
- Department of Biology, The Catholic University of America, 620 Michigan Ave, Washington, DC 20064, USA.
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Machen AJ, Fisher MT, Freudenthal BD. Anthrax toxin translocation complex reveals insight into the lethal factor unfolding and refolding mechanism. Sci Rep 2021; 11:13038. [PMID: 34158520 PMCID: PMC8219829 DOI: 10.1038/s41598-021-91596-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 05/27/2021] [Indexed: 11/09/2022] Open
Abstract
Translocation is essential to the anthrax toxin mechanism. Protective antigen (PA), the binding component of this AB toxin, forms an oligomeric pore that translocates lethal factor (LF) or edema factor, the active components of the toxin, into the cell. Structural details of the translocation process have remained elusive despite their biological importance. To overcome the technical challenges of studying translocation intermediates, we developed a method to immobilize, transition, and stabilize anthrax toxin to mimic important physiological steps in the intoxication process. Here, we report a cryoEM snapshot of PApore translocating the N-terminal domain of LF (LFN). The resulting 3.3 Å structure of the complex shows density of partially unfolded LFN near the canonical PApore binding site. Interestingly, we also observe density consistent with an α helix emerging from the 100 Å β barrel channel suggesting LF secondary structural elements begin to refold in the pore channel. We conclude the anthrax toxin β barrel aids in efficient folding of its enzymatic payload prior to channel exit. Our hypothesized refolding mechanism has broader implications for pore length of other protein translocating toxins.
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Affiliation(s)
- Alexandra J Machen
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Mark T Fisher
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA.
| | - Bret D Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA.
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Purde V, Kudryashova E, Heisler DB, Shakya R, Kudryashov DS. Intein-mediated cytoplasmic reconstitution of a split toxin enables selective cell ablation in mixed populations and tumor xenografts. Proc Natl Acad Sci U S A 2020; 117:22090-22100. [PMID: 32839344 PMCID: PMC7486740 DOI: 10.1073/pnas.2006603117] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The application of proteinaceous toxins for cell ablation is limited by their high on- and off-target toxicity, severe side effects, and a narrow therapeutic window. The selectivity of targeting can be improved by intein-based toxin reconstitution from two dysfunctional fragments provided their cytoplasmic delivery via independent, selective pathways. While the reconstitution of proteins from genetically encoded elements has been explored, exploiting cell-surface receptors for boosting selectivity has not been attained. We designed a robust splitting algorithm and achieved reliable cytoplasmic reconstitution of functional diphtheria toxin from engineered intein-flanked fragments upon receptor-mediated delivery of one of them to the cells expressing the counterpart. Retargeting the delivery machinery toward different receptors overexpressed in cancer cells enables selective ablation of specific subpopulations in mixed cell cultures. In a mouse model, the transmembrane delivery of a split-toxin construct potently inhibits the growth of xenograft tumors expressing the split counterpart. Receptor-mediated delivery of engineered split proteins provides a platform for precise therapeutic and experimental ablation of tumors or desired cell populations while also greatly expanding the applicability of the intein-based protein transsplicing.
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Affiliation(s)
- Vedud Purde
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210
| | - Elena Kudryashova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210;
| | - David B Heisler
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210
| | - Reena Shakya
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210
| | - Dmitri S Kudryashov
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210;
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210
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Baker CA, Schudel B, Chaudhari MI, Wu K, Dunford D, Singh AK, Rempe SB, Hatch AV. Nanoporous Hydrogels for the Observation of Anthrax Exotoxin Translocation Dynamics. ACS APPLIED MATERIALS & INTERFACES 2018; 10:13342-13349. [PMID: 29595948 DOI: 10.1021/acsami.8b01871] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The ability to observe lethal anthrax exotoxins translocating through size-constricting nanopores in vitro, combined with detailed sequence and structural data, has aided in elucidated mechanisms of exotoxin cell entry and toxicity. However, due to limited observations of anthrax exotoxins translocating through protective antigen nanopores in vitro and the instability of protective antigen-functionalized suspended lipid bilayers, questions remain regarding the native mechanisms of cell entry. Nanoporous hydrogel membranes offer a robust tool for studying protein translocation with ensemble measurements that complement conventional single-molecule translocation measurements. Here, we utilize nanoporous hydrogel membranes to assess the translocation of full-length anthrax lethal and edema factors through nanopores similar in diameter to protective antigen translocons. We find that, relative to globular serum and other proteins that do not translocate natively through nanopores, anthrax exotoxins demonstrate significantly reduced barriers to pore entry. Computed free-energy barriers to the unfolding of proteins and the dissociation of macromolecular complexes are generally found to coincide with translocation. Finally, a nanopore-blocking strategy is developed that utilizes nonspecific synthetic peptide constructs and effectively prevents LF translocation within the nanoporous hydrogel.
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Affiliation(s)
- Christopher A Baker
- Department of Chemistry , University of Tennessee , Knoxville , Tennessee 37996 , United States
| | - Ben Schudel
- Natera , San Carlos , California 94070 , United States
| | - Mangesh I Chaudhari
- Center for Biological and Engineering Sciences , Sandia National Laboratories , Albuquerque , New Mexico 87185 , United States
| | - Kerrie Wu
- Massachusetts Institute of Technology , Cambridge , Massachusetts 02129 , United States
| | - Derek Dunford
- University of Utah , Salt Lake City , Utah 84112 , United States
| | - Anup K Singh
- Center for Biological and Engineering Sciences , Sandia National Laboratories , Albuquerque , New Mexico 87185 , United States
| | - Susan B Rempe
- Center for Biological and Engineering Sciences , Sandia National Laboratories , Albuquerque , New Mexico 87185 , United States
| | - Anson V Hatch
- Center for Biological and Engineering Sciences , Sandia National Laboratories , Albuquerque , New Mexico 87185 , United States
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Asymmetric Cryo-EM Structure of Anthrax Toxin Protective Antigen Pore with Lethal Factor N-Terminal Domain. Toxins (Basel) 2017; 9:toxins9100298. [PMID: 28937604 PMCID: PMC5666345 DOI: 10.3390/toxins9100298] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 09/18/2017] [Accepted: 09/19/2017] [Indexed: 11/17/2022] Open
Abstract
The anthrax lethal toxin consists of protective antigen (PA) and lethal factor (LF). Understanding both the PA pore formation and LF translocation through the PA pore is crucial to mitigating and perhaps preventing anthrax disease. To better understand the interactions of the LF-PA engagement complex, the structure of the LFN-bound PA pore solubilized by a lipid nanodisc was examined using cryo-EM. CryoSPARC was used to rapidly sort particle populations of a heterogeneous sample preparation without imposing symmetry, resulting in a refined 17 Å PA pore structure with 3 LFN bound. At pH 7.5, the contributions from the three unstructured LFN lysine-rich tail regions do not occlude the Phe clamp opening. The open Phe clamp suggests that, in this translocation-compromised pH environment, the lysine-rich tails remain flexible and do not interact with the pore lumen region.
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