1
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Krone L, Mahankali S, Geiger T. Cytolysin A is an intracellularly induced and secreted cytotoxin of typhoidal Salmonella. Nat Commun 2024; 15:8414. [PMID: 39341826 PMCID: PMC11438861 DOI: 10.1038/s41467-024-52745-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 09/20/2024] [Indexed: 10/01/2024] Open
Abstract
Typhoidal Salmonella enterica serovars, such as Typhi and Paratyphi A, cause severe systemic infections, thereby posing a significant threat as human-adapted pathogens. This study focuses on cytolysin A (ClyA), a virulence factor essential for bacterial dissemination within the human body. We show that ClyA is exclusively expressed by intracellular S. Paratyphi A within the Salmonella-containing vacuole (SCV), regulated by the PhoP/Q system and SlyA. ClyA localizes in the bacterial periplasm, suggesting potential secretion. Deletion of TtsA, an essential Type 10 Secretion System component, completely abolishes intracellular ClyA detection and its presence in host cell supernatants. Host cells infected with wild-type S. Paratyphi A contain substantial ClyA, with supernatants capable of lysing neighboring cells. Notably, ClyA selectively lyses macrophages and erythrocytes while sparing epithelial cells. These findings identify ClyA as an intracellularly induced cytolysin, dependent on the SCV environment and secreted via a Type 10 Secretion System, with specific cytolytic activity.
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Affiliation(s)
- Lena Krone
- Max von Pettenkofer-Institute, Chair for Medical Microbiology and Hygiene, Ludwig-Maximilians-Universität München (LMU Munich), Munich, Germany
| | - Srujita Mahankali
- Max von Pettenkofer-Institute, Chair for Medical Microbiology and Hygiene, Ludwig-Maximilians-Universität München (LMU Munich), Munich, Germany
| | - Tobias Geiger
- Max von Pettenkofer-Institute, Chair for Medical Microbiology and Hygiene, Ludwig-Maximilians-Universität München (LMU Munich), Munich, Germany.
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2
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Sultana OF, Hia RA, Reddy PH. A Combinational Therapy for Preventing and Delaying the Onset of Alzheimer's Disease: A Focus on Probiotic and Vitamin Co-Supplementation. Antioxidants (Basel) 2024; 13:202. [PMID: 38397800 PMCID: PMC10886126 DOI: 10.3390/antiox13020202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Revised: 01/27/2024] [Accepted: 02/02/2024] [Indexed: 02/25/2024] Open
Abstract
Alzheimer's disease is a progressive neurodegenerative disorder with a complex etiology, and effective interventions to prevent or delay its onset remain a global health challenge. In recent years, there has been growing interest in the potential role of probiotic and vitamin supplementation as complementary strategies for Alzheimer's disease prevention. This review paper explores the current scientific literature on the use of probiotics and vitamins, particularly vitamin A, D, E, K, and B-complex vitamins, in the context of Alzheimer's disease prevention and management. We delve into the mechanisms through which probiotics may modulate gut-brain interactions and neuroinflammation while vitamins play crucial roles in neuronal health and cognitive function. The paper also examines the collective impact of this combinational therapy on reducing the risk factors associated with Alzheimer's disease, such as oxidative stress, inflammation, and gut dysbiosis. By providing a comprehensive overview of the existing evidence and potential mechanisms, this review aims to shed light on the promise of probiotic and vitamin co-supplementation as a multifaceted approach to combat Alzheimer's disease, offering insights into possible avenues for future research and clinical application.
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Affiliation(s)
- Omme Fatema Sultana
- Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA;
| | - Raksa Andalib Hia
- Nutritional Sciences Department, College of Human Sciences, Texas Tech University, Lubbock, TX 79409, USA;
| | - P. Hemachandra Reddy
- Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA;
- Nutritional Sciences Department, College of Human Sciences, Texas Tech University, Lubbock, TX 79409, USA;
- Public Health Department of Graduate School of Biomedical Sciences, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Department of Speech, Language and Hearing Sciences, School Health Professions, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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3
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Das A, K V, S SD, Mahendran KR. Synthetic α-Helical Nanopore Reactor for Chemical Sensing. JACS AU 2023; 3:2467-2477. [PMID: 37772177 PMCID: PMC10523496 DOI: 10.1021/jacsau.3c00221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 07/15/2023] [Accepted: 07/18/2023] [Indexed: 09/30/2023]
Abstract
The use of nanopores for the single-molecule sensing of folded proteins and biomacromolecules has recently gained attention. Here, we introduce a simplified synthetic α-helical transmembrane pore, pPorA, as a nanoreactor and sensor that exhibits functional versatility comparable to that of engineered protein and DNA nanopores. The pore, built from the assembly of synthetic 40-amino-acid-long peptides, is designed to contain cysteine residues within the lumen and at the pore terminus for site-specific chemical modification probed using single-channel electrical recordings. The reaction of the pore with differently charged activated thiol reagents was studied, wherein positively charged reagents electrophoretically driven into the pore resulted in pore blocking in discrete steps upon covalent bond formation. The asymmetric blockage patterns resulting from cis and trans-side addition of reagents reveal the pore orientation in the lipid membrane. Furthermore, activated PEG thiols covalently blocked the pores over a longer duration in a charge-independent manner, establishing the large diameter and orientation of the formed pores. While the covalent binding of thiol reagents caused a drop in the pore conductance, cationic cyclic octasaccharides produced time-resolved translocation events, confirming the structural flexibility and tunability of the pores. The ability of the pore to accommodate large analytes and the considerable current amplitude variation following bond formation events are promising for developing platforms to resolve multistep chemical reactions at the single-molecule level for applications in synthetic nanobiotechnology.
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Affiliation(s)
- Anjali
Devi Das
- Membrane Biology Laboratory, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India 695014
| | - Vidhu K
- Membrane Biology Laboratory, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India 695014
| | - Smitha Devi S
- Membrane Biology Laboratory, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India 695014
| | - Kozhinjampara R Mahendran
- Membrane Biology Laboratory, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India 695014
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4
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Wang HC, Lin SJ, Wang HC, Kumar R, Le PT, Leu JH. A bacterial binary toxin system that kills both insects and aquatic crustaceans: Photorhabdus insect-related toxins A and B. PLoS Pathog 2023; 19:e1011330. [PMID: 37141203 PMCID: PMC10159206 DOI: 10.1371/journal.ppat.1011330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023] Open
Abstract
Photorhabdus insect-related toxins A and B (PirA and PirB) were first recognized as insecticidal toxins from Photorhabdus luminescens. However, subsequent studies showed that their homologs from Vibrio parahaemolyticus also play critical roles in the pathogenesis of acute hepatopancreatic necrosis disease (AHPND) in shrimps. Based on the structural features of the PirA/PirB toxins, it was suggested that they might function in the same way as a Bacillus thuringiensis Cry pore-forming toxin. However, unlike Cry toxins, studies on the PirA/PirB toxins are still scarce, and their cytotoxic mechanism remains to be clarified. In this review, based on our studies of V. parahaemolyticus PirAvp/PirBvp, we summarize the current understanding of the gene locations, expression control, activation, and cytotoxic mechanism of this type of toxin. Given the important role these toxins play in aquatic disease and their potential use in pest control applications, we also suggest further topics for research. We hope the information presented here will be helpful for future PirA/PirB studies.
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Affiliation(s)
- Hao-Ching Wang
- Graduate Institute of Translational Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan, Republic of China
- The PhD Program for Translational Medicine, College of Medical Science and Technology, Taipei Medical University and Academia Sinica, Taipei, Taiwan, Republic of China
- International Center for the Scientific Development of Shrimp Aquaculture, National Cheng Kung University, Tainan, Taiwan, Republic of China
| | - Shin-Jen Lin
- International Center for the Scientific Development of Shrimp Aquaculture, National Cheng Kung University, Tainan, Taiwan, Republic of China
| | - Han-Ching Wang
- International Center for the Scientific Development of Shrimp Aquaculture, National Cheng Kung University, Tainan, Taiwan, Republic of China
- Department of Biotechnology and Bioindustry Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan, Republic of China
| | - Ramya Kumar
- International Center for the Scientific Development of Shrimp Aquaculture, National Cheng Kung University, Tainan, Taiwan, Republic of China
- Department of Biotechnology and Bioindustry Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan, Republic of China
| | - Phuoc Thien Le
- Graduate Institute of Translational Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan, Republic of China
| | - Jiann-Horng Leu
- Institute of Marine Biology, National Taiwan Ocean University, Keelung, Taiwan, Republic of China
- Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung, Taiwan, Republic of China
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5
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Ojha S, Patil N, Jain M, Kole C, Kaushik P. Probiotics for Neurodegenerative Diseases: A Systemic Review. Microorganisms 2023; 11:microorganisms11041083. [PMID: 37110506 PMCID: PMC10140855 DOI: 10.3390/microorganisms11041083] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 04/12/2023] [Accepted: 04/18/2023] [Indexed: 04/29/2023] Open
Abstract
Neurodegenerative disorders (ND) are a group of conditions that affect the neurons in the brain and spinal cord, leading to their degeneration and eventually causing the loss of function in the affected areas. These disorders can be caused by a range of factors, including genetics, environmental factors, and lifestyle choices. Major pathological signs of these diseases are protein misfolding, proteosomal dysfunction, aggregation, inadequate degradation, oxidative stress, free radical formation, mitochondrial dysfunctions, impaired bioenergetics, DNA damage, fragmentation of Golgi apparatus neurons, disruption of axonal transport, dysfunction of neurotrophins (NTFs), neuroinflammatory or neuroimmune processes, and neurohumoral symptoms. According to recent studies, defects or imbalances in gut microbiota can directly lead to neurological disorders through the gut-brain axis. Probiotics in ND are recommended to prevent cognitive dysfunction, which is a major symptom of these diseases. Many in vivo and clinical trials have revealed that probiotics (Lactobacillus acidophilus, Bifidobacterium bifidum, and Lactobacillus casei, etc.) are effective candidates against the progression of ND. It has been proven that the inflammatory process and oxidative stress can be modulated by modifying the gut microbiota with the help of probiotics. As a result, this study provides an overview of the available data, bacterial variety, gut-brain axis defects, and probiotics' mode of action in averting ND. A literature search on particular sites, including PubMed, Nature, and Springer Link, has identified articles that might be pertinent to this subject. The search contains the following few groups of terms: (1) Neurodegenerative disorders and Probiotics OR (2) Probiotics and Neurodegenerative disorders. The outcomes of this study aid in elucidating the relationship between the effects of probiotics on different neurodegenerative disorders. This systematic review will assist in discovering new treatments in the future, as probiotics are generally safe and cause mild side effects in some cases in the human body.
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Affiliation(s)
- Sandhya Ojha
- Cell & Developmental Biology Laboratory, Centre of Research for Development, Parul University, Vadodara 391760, India
- Department of Life Sciences, Parul Institute of Applied Sciences, Parul University, Vadodara 391760, India
| | - Nil Patil
- Cell & Developmental Biology Laboratory, Centre of Research for Development, Parul University, Vadodara 391760, India
- Department of Life Sciences, Parul Institute of Applied Sciences, Parul University, Vadodara 391760, India
| | - Mukul Jain
- Cell & Developmental Biology Laboratory, Centre of Research for Development, Parul University, Vadodara 391760, India
- Department of Life Sciences, Parul Institute of Applied Sciences, Parul University, Vadodara 391760, India
| | | | - Prashant Kaushik
- Instituto de Conservacióny Mejora de la Agrodiversidad Valenciana, Universitat Politècnica de València, 46022 Valencia, Spain
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6
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Yang Z, Hua L, Yang M, Li W, Ren Z, Zheng X, Chen H, Long Q, Bai H, Huang W, Ma Y. Polymerized porin as a novel delivery platform for coronavirus vaccine. J Nanobiotechnology 2022; 20:260. [PMID: 35672856 PMCID: PMC9171476 DOI: 10.1186/s12951-022-01469-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 05/20/2022] [Indexed: 11/10/2022] Open
Abstract
Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), seriously threatens human life and health. The correct folding and polymerization of the receptor-binding domain (RBD) protein of coronavirus in Escherichia coli may reduce the cost of SARS-CoV-2 vaccines. In this study, we constructed this nanopore by using the principle of ClyA porin polymerization triggered by the cell membrane. We used surfactants to "pick" the ClyA-RBD nanopore from the bacterial outer membrane. More importantly, the polymerized RBD displayed on the ClyA-RBD polymerized porin (RBD-PP) already displays some correct spatial conformational epitopes that can induce neutralizing antibodies. The nanostructures of RBD-PP can target lymph nodes and promote antigen uptake and processing by dendritic cells, thereby effectively eliciting the production of anti-SARS-CoV-2 neutralizing antibodies, systemic cellular immune responses, and memory T cells. We applied this PP-based vaccine platform to fabricate an RBD-based subunit vaccine against SARS-CoV-2, which will provide a foundation for the development of inexpensive coronavirus vaccines. The development of a novel vaccine delivery system is an important part of innovative drug research. This novel PP-based vaccine platform is likely to have additional applications, including other viral vaccines, bacterial vaccines, tumor vaccines, drug delivery, and disease diagnosis.
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Affiliation(s)
- Zhongqian Yang
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, 650031, China
| | - Liangqun Hua
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, 650031, China
- Yunnan University, Kunming, 650091, China
| | - Mengli Yang
- National Kunming High-Level Biosafety Primate Research Center, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, 650031, China
| | - Weiran Li
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, 650031, China
| | - Zhaoling Ren
- The Second Affiliated Hospital of Kunming Medical University, Kunming, 650033, China
| | - Xiao Zheng
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, 650031, China
- Yunnan University, Kunming, 650091, China
| | - Haoqian Chen
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, 650031, China
- Yunnan Minzu University, Kunming, 650504, China
| | - Qiong Long
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, 650031, China
| | - Hongmei Bai
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, 650031, China
| | - Weiwei Huang
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, 650031, China.
| | - Yanbing Ma
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, 650031, China.
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7
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Sun Z, Zhou N, Zhang W, Xu Y, Yao YF. Dual role of CsrA in regulating the hemolytic activity of Escherichia coli O157:H7. Virulence 2022; 13:859-874. [PMID: 35609307 PMCID: PMC9132389 DOI: 10.1080/21505594.2022.2073023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Post-transcriptional global carbon storage regulator A (CsrA) is a sequence-specific RNA-binding protein involved in the regulation of multiple bacterial processes. Hemolysin is an important virulence factor in the enterohemorrhagic Escherichia coli O157:H7 (EHEC). Here, we show that CsrA plays a dual role in the regulation of hemolysis in EHEC. CsrA significantly represses plasmid-borne enterohemolysin (EhxA)-mediated hemolysis and activates chromosome-borne hemolysin E (HlyE)-mediated hemolysis through different mechanisms. RNA structure prediction revealed a well-matched stem-loop structure with two potential CsrA binding sites located on the 5' untranslated region (UTR) of ehxB, which encodes a translocator required for EhxA secretion. CsrA inhibits EhxA secretion by directly binding to the RNA leader sequence of ehxB to repress its expression in two different ways: CsrA either binds to the Shine–Dalgarno sequence of ehxB to block ribosome access or to ehxB transcript to promote its mRNA decay. The predicted CsrA-binding site 1 of ehxB is essential for its regulation. There is a single potential CsrA-binding site at the 5'-end of the hlyE transcript, and its mutation completely abolishes CsrA-dependent activation. CsrA can also stabilize hlyE mRNA by directly binding to its 5' UTR. Overall, our results indicate that CsrA acts as a hemolysis modulator to regulate pathogenicity under certain conditions.
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Affiliation(s)
- Zhibin Sun
- Laboratory of Bacterial Pathogenesis, Department of Microbiology and Immunology, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Ning Zhou
- Laboratory of Bacterial Pathogenesis, Department of Microbiology and Immunology, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wenting Zhang
- Laboratory of Bacterial Pathogenesis, Department of Microbiology and Immunology, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yan Xu
- Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Yu-Feng Yao
- Laboratory of Bacterial Pathogenesis, Department of Microbiology and Immunology, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Department of Infectious Diseases, Shanghai Ruijin Hospital, Shanghai, China.,Shanghai Key Laboratory of Emergency Prevention, Diagnosis and Treatment of Respiratory Infectious Diseases, Shanghai, China
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8
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Zhang M, Liu J, Yin Z, Zhang L. Phylogenetic and protein prediction analysis reveals the taxonomically diverse distribution of virulence factors in Bacillus cereus strains. PLoS One 2022; 17:e0262974. [PMID: 35588435 PMCID: PMC9119529 DOI: 10.1371/journal.pone.0262974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 04/21/2022] [Indexed: 12/04/2022] Open
Abstract
Bacillus cereus is a food contaminant with widely varying enterotoxic potential due to its virulence proteins. In this article, phylogenetic analysis of the amino acid sequences from the whole-genomes of 41 strains, evolutionary distance calculation of the amino acid sequences of the virulence genes, and functional and structural predictions of the virulence proteins were performed to reveal the taxonomically diverse distribution of virulence factors. The genome evolution of the strains showed a clustering trend based on the protein-coding virulence genes. The strains of B. cereus have evolved into non-toxic risk and toxic risk clusters with medium-high- and medium-low-risk subclusters. The evolutionary transfer distances of incomplete virulence genes relative to housekeeping genes were greater than those of complete virulence genes, and the distance values of HblACD were higher than those of nheABC and CytK among the complete virulence genes. Cytoplasmic localization was impossible for all the virulence proteins, and NheB, NheC, Hbl-B, and Hbl-L1 were predicted to be extracellular. Nhe and Hbl proteins except CytK had similar spatial structures. The predicted structures of Nhe and Hbl mainly showed ‘head’ and ‘tail’ domains. The ‘head’ of NheA and Hbl-B, including two α-helices separated by β-tongue strands, might play a special role in the formation of Nhe trimers and Hbl trimers, respectively. The ‘cap’ of CytK, which includes two ‘latches’ with many β-sheets, formed a β-barrel structure with pores, and a ‘rim’ balanced the structure. The evolution of B. cereus strains showed a clustering tendency based on the protein-coding virulence genes, and the complete virulence-gene operon combination had higher relative genetic stability. The beta-tongue or latch associated with β-sheet folding might play an important role in the binding of virulence structures and pore-forming toxins in B. cereus.
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Affiliation(s)
- Ming Zhang
- School of Yunkang Medicine and Health, Nanfang College, Guangzhou, Guangdong, China
| | - Jun Liu
- School of Yunkang Medicine and Health, Nanfang College, Guangzhou, Guangdong, China
| | - Zhenzhen Yin
- School of Yunkang Medicine and Health, Nanfang College, Guangzhou, Guangdong, China
- * E-mail: (ZY); (LZ)
| | - Li Zhang
- School of Life Science, Liaoning University, Shenyang, Liaoning, China
- * E-mail: (ZY); (LZ)
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Denuga S, Whelan DE, O'Neill SP, Johnson RP. Capture and analysis of double‐stranded DNA with the α‐hemolysin nanopore: Fundamentals and applications. ELECTROCHEMICAL SCIENCE ADVANCES 2022. [DOI: 10.1002/elsa.202200001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Affiliation(s)
| | | | | | - Robert P. Johnson
- School of Chemistry University College Dublin Ireland
- UCD‐Centre for Food Safety University College Dublin Dublin Ireland
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10
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Jessberger N, Diedrich R, Janowski R, Niessing D, Märtlbauer E. Presence and function of Hbl B', the fourth protein component encoded by the hbl operon in Bacillus cereus. Virulence 2022; 13:483-501. [PMID: 35291913 PMCID: PMC8932913 DOI: 10.1080/21505594.2022.2046951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The genes hblC, hblD and hblA encode the components Hbl L2, L1 and B of the pore forming enterotoxin haemolysin BL of Bacillus cereus. Two variants of the operon existand the more common one additionally contains hblB downstream of hblCDA. Up to now, it was completely unclear whether the corresponding protein, Hbl B', is widely expressed among B. cereus strains and if it has a distinct function. In the present study, it was shown that the hblB gene is indeed expressed and the Hbl B' protein is secreted by nearly all analysed B. cereus strains. For the latter, a detection system was developed based on monoclonal antibody 11A5. Further, a distinct reduction of cytotoxic and haemolytic activity was observed when recombinant (r)Hbl B' was applied simultaneously with L2, L1 and B. This effect was due to direct interaction of rHbl B' with L1. D-6B. cereusAltogether, we present the first simple tool for the detection of Hbl B' in B. cereus culture supernatants. Moreover, an important regulatory function of Hbl B' in the mechanism of Hbl was determined, which is best described as an additional control of complex formation, balancing the amounts of Hbl B-L1 complexes and the corresponding free subunits.
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Affiliation(s)
- Nadja Jessberger
- Institute for Food Quality and Food Safety, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Richard Diedrich
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Oberschleißheim, Germany
| | - Robert Janowski
- Institute of Structural Biology, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany
| | - Dierk Niessing
- Institute of Structural Biology, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany.,Institute of Pharmaceutical Biotechnology, Ulm University, Ulm, Germany
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Oberschleißheim, Germany
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Keith BA, Harding JCS, Loewen ME. Mutational analysis of TlyA from Brachyspira hampsonii reveals two key residues conserved in pathogenic bacteria responsible for oligomerization and hemolytic activity. Biochim Biophys Acta Gen Subj 2022; 1866:130045. [PMID: 34715264 DOI: 10.1016/j.bbagen.2021.130045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 10/07/2021] [Accepted: 10/22/2021] [Indexed: 12/01/2022]
Abstract
BACKGROUND TlyA proteins are expressed in a variety of pathogenic bacteria and possess dual hemolytic and ribosomal RNA methyltransferase functions. While the mechanism of TlyA mediated rRNA methylation is well understood, relatively little is known about the mechanism of TlyA induced hemolysis. METHODS TlyA protein from the pig pathogen Brachyspira hampsonii was heterologously expressed and purified from an E. coli host. Hemolytic activity and rRNA methylation were assessed in vitro. Site-directed mutagenesis was used to mutate amino acids believed to be involved in TlyA mediated hemolysis. RESULTS Purified TlyA-His protein exhibited both hemolytic and rRNA methyltransferase activities in vitro, with partial inhibition of hemolysis observed under reducing conditions. Mutation of cysteine 80 to alanine impaired hemolytic activity. A C27A/C93A mutant was capable of dimerizing under non-reducing conditions, indicating that a C80-C80 disulfide bond is involved in TlyA oligomerization. A mutation conserved in several avirulent Brachyspira species (S9K) completely abolished hemolytic activity of TlyA. This loss of activity was attributed to impaired oligomerization in the S9K mutant, as assessed by ITC and size-exclusion chromatography experiments. CONCLUSIONS Oligomeric assembly and hemolytic activity of TlyA from Brachyspira hampsonii is dependent on the formation of an intermolecular C80-C80 disulfide bond and noncovalent interactions involving serine 9. The conservation of these amino acids in TlyA proteins from pathogenic bacteria suggests a correlation between tlyA gene mutations and bacterial virulence. GENERAL SIGNIFICANCE Our results further elucidate the mechanisms underlying TlyA mediated hemolysis and provide evidence of a conserved mechanism of oligomerization for TlyA family proteins.
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Affiliation(s)
- Brandon A Keith
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada
| | - John C S Harding
- Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Matthew E Loewen
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
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12
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Cytolysin A (ClyA): A Bacterial Virulence Factor with Potential Applications in Nanopore Technology, Vaccine Development, and Tumor Therapy. Toxins (Basel) 2022; 14:toxins14020078. [PMID: 35202106 PMCID: PMC8880466 DOI: 10.3390/toxins14020078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 01/14/2022] [Accepted: 01/18/2022] [Indexed: 12/26/2022] Open
Abstract
Cytolysin A (ClyA) is a pore-forming toxin that is produced by some bacteria from the Enterobacteriaceae family. This review provides an overview of the current state of knowledge regarding ClyA, including the prevalence of the encoding gene and its transcriptional regulation, the secretion pathway used by the protein, and the mechanism of protein assembly, and highlights potential applications of ClyA in biotechnology. ClyA expression is regulated at the transcriptional level, primarily in response to environmental stressors, and ClyA can exist stably both as a soluble monomer and as an oligomeric membrane complex. At high concentrations, ClyA induces cytolysis, whereas at low concentrations ClyA can affect intracellular signaling. ClyA is secreted in outer membrane vesicles (OMVs), which has important implications for biotechnology applications. For example, the native pore-forming ability of ClyA suggests that it could be used as a component of nanopore-based technologies, such as sequencing platforms. ClyA has also been exploited in vaccine development owing to its ability to present antigens on the OMV surface and provoke a robust immune response. In addition, ClyA alone or OMVs carrying ClyA fusion proteins have been investigated for their potential use as anti-tumor agents.
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Chatterjee R, Chowdhury AR, Mukherjee D, Chakravortty D. Lipid larceny: channelizing host lipids for establishing successful pathogenesis by bacteria. Virulence 2021; 12:195-216. [PMID: 33356849 PMCID: PMC7808437 DOI: 10.1080/21505594.2020.1869441] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 12/03/2020] [Accepted: 12/17/2020] [Indexed: 12/16/2022] Open
Abstract
Lipids are complex organic compounds made up of carbon, oxygen, and hydrogen. These play a diverse and intricate role in cellular processes like membrane trafficking, protein sorting, signal transduction, and bacterial infections. Both Gram-positive bacteria (Staphylococcus sp., Listeria monocytogenes, etc.) and Gram-negative bacteria (Chlamydia sp., Salmonella sp., E. coli, etc.) can hijack the various host-lipids and utilize them structurally as well as functionally to mount a successful infection. The pathogens can deploy with various arsenals to exploit host membrane lipids and lipid-associated receptors as an attachment for toxins' landing or facilitate their entry into the host cellular niche. Bacterial species like Mycobacterium sp. can also modulate the host lipid metabolism to fetch its carbon source from the host. The sequential conversion of host membrane lipids into arachidonic acid and prostaglandin E2 due to increased activity of cPLA-2 and COX-2 upon bacterial infection creates immunosuppressive conditions and facilitates the intracellular growth and proliferation of bacteria. However, lipids' more debatable role is that they can also be a blessing in disguise. Certain host-lipids, especially sphingolipids, have been shown to play a crucial antibacterial role and help the host in combating the infections. This review shed light on the detailed role of host lipids in bacterial infections and the current understanding of the lipid in therapeutics. We have also discussed potential prospects and the need of the hour to help us cope in this race against deadly pathogens and their rapidly evolving stealthy virulence strategies.
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Affiliation(s)
- Ritika Chatterjee
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Atish Roy Chowdhury
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Debapriya Mukherjee
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Dipshikha Chakravortty
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
- Centre for Biosystems Science and Engineering, Indian Institute of Science, Bangalore, India
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14
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Benke S, Holla A, Wunderlich B, Soranno A, Nettels D, Schuler B. Combining Rapid Microfluidic Mixing and Three-Color Single-Molecule FRET for Probing the Kinetics of Protein Conformational Changes. J Phys Chem B 2021; 125:6617-6628. [PMID: 34125545 DOI: 10.1021/acs.jpcb.1c02370] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Single-molecule Förster resonance energy transfer (FRET) is well suited for studying the kinetics of protein conformational changes, owing to its high sensitivity and ability to resolve individual subpopulations in heterogeneous systems. However, the most common approach employing two fluorophores can only monitor one distance at a time, and the use of three fluorophores for simultaneously monitoring multiple distances has largely been limited to equilibrium fluctuations. Here we show that three-color single-molecule FRET can be combined with rapid microfluidic mixing to investigate conformational changes in a protein from milliseconds to minutes. In combination with manual mixing, we extended the kinetics to 1 h, corresponding to a total range of 5 orders of magnitude in time. We studied the monomer-to-protomer conversion of the pore-forming toxin cytolysin A (ClyA), one of the largest protein conformational transitions known. Site-specific labeling of ClyA with three fluorophores enabled us to follow the kinetics of three intramolecular distances at the same time and revealed a previously undetected intermediate. The combination of three-color single-molecule FRET with rapid microfluidic mixing thus provides an approach for probing the mechanisms of complex biomolecular processes with high time resolution.
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Affiliation(s)
- Stephan Benke
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Andrea Holla
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Bengt Wunderlich
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Andrea Soranno
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.,Department of Biochemistry and Molecular Biophysics, Center for Science and Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Daniel Nettels
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Benjamin Schuler
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.,Department of Physics, University of Zurich, Winterthurerstrasse. 190, 8057 Zurich, Switzerland
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15
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Banerji R, Karkee A, Kanojiya P, Saroj SD. Pore-forming toxins of foodborne pathogens. Compr Rev Food Sci Food Saf 2021; 20:2265-2285. [PMID: 33773026 DOI: 10.1111/1541-4337.12737] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 02/01/2021] [Accepted: 02/08/2021] [Indexed: 01/04/2023]
Abstract
Pore-forming toxins (PFTs) are water-soluble molecules that have been identified as the most crucial virulence factors during bacterial pathogenesis. PFTs disrupt the host cell membrane to internalize or to deliver other bacterial or virulence factors for establishing infections. Disruption of the host cell membrane by PFTs can lead to uncontrollable exchanges between the extracellular and the intracellular matrix, thereby disturbing the cellular homeostasis. Recent studies have provided insights into the molecular mechanism of PFTs during pathogenesis. Evidence also suggests the activation of several signal transduction pathways in the host cell on recognition of PFTs. Additionally, numerous distinctive host defense mechanisms as well as membrane repair mechanisms have been reported; however, studies reveal that PFTs aid in host immune evasion of the bacteria through numerous pathways. PFTs have been primarily associated with foodborne pathogens. Infection and death from diseases by consuming contaminated food are a constant threat to public health worldwide, affecting socioeconomic development. Moreover, the emergence of new foodborne pathogens has led to the rise of bacterial antimicrobial resistance affecting the population. Hence, this review focuses on the role of PFTs secreted by foodborne pathogens. The review highlights the molecular mechanism of foodborne bacterial PFTs, assisting bacterial survival from the host immune responses and understanding the downstream mechanism in the activation of various signaling pathways in the host upon PFT recognition. PFT research is a remarkable and an important field for exploring novel and broad applications of antimicrobial compounds as therapeutics.
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Affiliation(s)
- Rajashri Banerji
- Symbiosis School of Biological Sciences, Symbiosis International (Deemed University), Pune, India
| | - Astha Karkee
- Symbiosis School of Biological Sciences, Symbiosis International (Deemed University), Pune, India
| | - Poonam Kanojiya
- Symbiosis School of Biological Sciences, Symbiosis International (Deemed University), Pune, India
| | - Sunil D Saroj
- Symbiosis School of Biological Sciences, Symbiosis International (Deemed University), Pune, India
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16
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Churchill-Angus AM, Schofield THB, Marlow TR, Sedelnikova SE, Wilson JS, Rafferty JB, Baker PJ. Characterisation of a tripartite α-pore forming toxin from Serratia marcescens. Sci Rep 2021; 11:6447. [PMID: 33742033 PMCID: PMC7979752 DOI: 10.1038/s41598-021-85726-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 03/03/2021] [Indexed: 01/31/2023] Open
Abstract
Tripartite members of the ClyA family of α-PFTs have recently been identified in a number of pathogenic Gram-negative bacteria, including the human pathogen Serratia marcescens. Structures of a Gram-negative A component and a tripartite α-PFT complete pore are unknown and a mechanism for pore formation is still uncertain. Here we characterise the tripartite SmhABC toxin from S. marcescens and propose a mechanism of pore assembly. We present the structure of soluble SmhA, as well as the soluble and pore forms of SmhB. We show that the β-tongue soluble structure is well conserved in the family and propose two conserved latches between the head and tail domains that are broken on the soluble to pore conformational change. Using the structures of individual components, sequence analysis and docking predictions we illustrate how the A, B and C protomers would assemble on the membrane to produce a complete tripartite α-PFT pore.
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Affiliation(s)
- Alicia M Churchill-Angus
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, South Yorkshire, UK
| | - Thomas H B Schofield
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, South Yorkshire, UK
- Current address: Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Thomas R Marlow
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, South Yorkshire, UK
| | - Svetlana E Sedelnikova
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, South Yorkshire, UK
| | - Jason S Wilson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, South Yorkshire, UK
| | - John B Rafferty
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, South Yorkshire, UK
| | - Patrick J Baker
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, South Yorkshire, UK.
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17
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Parperis C, Wallace MI. Single-molecule imaging of pore-forming toxin dynamics in droplet interface bilayers. Methods Enzymol 2021; 649:431-459. [PMID: 33712195 DOI: 10.1016/bs.mie.2021.01.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Single-channel recording from pore-forming toxins (PFTs) provides a clear and direct molecular readout of toxin action. However to complete any mechanistic understanding of PFT behavior, this functional kinetic readout must be linked to the underlying changes in toxin structure, binding, conformation, or stoichiometry. Here we review how single-molecule imaging methods might be used to further our understanding of PFTs, and provide detailed practical guidance on the use of droplet interface bilayers as a method capable of examining both single-molecule fluorescence and single-channel electrical signals from PFTs.
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Affiliation(s)
- Christopher Parperis
- Department of Chemistry, Britannia House, King's College London, London, United Kingdom
| | - Mark I Wallace
- Department of Chemistry, Britannia House, King's College London, London, United Kingdom.
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18
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Wloka C, Galenkamp NS, van der Heide NJ, Lucas FLR, Maglia G. Strategies for enzymological studies and measurements of biological molecules with the cytolysin A nanopore. Methods Enzymol 2021; 649:567-585. [PMID: 33712200 DOI: 10.1016/bs.mie.2021.01.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Pore-forming toxins are used in a variety of biotechnological applications. Typically, individual membrane proteins are reconstituted in artificial lipid bilayers where they form water-filled nanoscale apertures (nanopores). When a voltage is applied, the ionic current passing through a nanopore can be used for example to sequence biopolymers, identify molecules, or to study chemical or enzymatic reactions at the single-molecule level. Here we present strategies for studying individual enzymes and measuring molecules, also in highly complex biological samples such as blood.
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Affiliation(s)
- Carsten Wloka
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen, The Netherlands.
| | - Nicole S Galenkamp
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Nieck J van der Heide
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Florian L R Lucas
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Giovanni Maglia
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen, The Netherlands.
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19
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Johnstone BA, Christie MP, Morton CJ, Parker MW. X-ray crystallography shines a light on pore-forming toxins. Methods Enzymol 2021; 649:1-46. [PMID: 33712183 DOI: 10.1016/bs.mie.2021.01.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A common form of cellular attack by pathogenic bacteria is to secrete pore-forming toxins (PFTs). Capable of forming transmembrane pores in various biological membranes, PFTs have also been identified in a diverse range of other organisms such as sea anemones, earthworms and even mushrooms and trees. The mechanism of pore formation by PFTs is associated with substantial conformational changes in going from the water-soluble to transmembrane states of the protein. The determination of the crystal structures for numerous PFTs has shed much light on our understanding of these proteins. Other than elucidating the atomic structural details of PFTs and the conformational changes that must occur for pore formation, crystal structures have revealed structural homology that has led to the discovery of new PFTs and new PFT families. Here we review some key crystallographic results together with complimentary approaches for studying PFTs. We discuss how these studies have impacted our understanding of PFT function and guided research into biotechnical applications.
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Affiliation(s)
- Bronte A Johnstone
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia
| | - Michelle P Christie
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia
| | - Craig J Morton
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia
| | - Michael W Parker
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia; St. Vincent's Institute of Medical Research, Fitzroy, VIC, Australia.
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20
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The Food Poisoning Toxins of Bacillus cereus. Toxins (Basel) 2021; 13:toxins13020098. [PMID: 33525722 PMCID: PMC7911051 DOI: 10.3390/toxins13020098] [Citation(s) in RCA: 113] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/14/2021] [Accepted: 01/25/2021] [Indexed: 12/13/2022] Open
Abstract
Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide cereulide, and the proteinaceous enterotoxins hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK), respectively. This review covers the current knowledge on distribution and genetic organization of the toxin genes, as well as mechanisms of enterotoxin gene regulation and toxin secretion. In this context, the exceptionally high variability of toxin production between single strains is highlighted. In addition, the mode of action of the pore-forming enterotoxins and their effect on target cells is described in detail. The main focus of this review are the two tripartite enterotoxin complexes Hbl and Nhe, but the latest findings on cereulide and CytK are also presented, as well as methods for toxin detection, and the contribution of further putative virulence factors to the diarrheal disease.
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21
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Crnković A, Srnko M, Anderluh G. Biological Nanopores: Engineering on Demand. Life (Basel) 2021; 11:life11010027. [PMID: 33466427 PMCID: PMC7824896 DOI: 10.3390/life11010027] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 12/24/2020] [Accepted: 12/31/2020] [Indexed: 12/17/2022] Open
Abstract
Nanopore-based sensing is a powerful technique for the detection of diverse organic and inorganic molecules, long-read sequencing of nucleic acids, and single-molecule analyses of enzymatic reactions. Selected from natural sources, protein-based nanopores enable rapid, label-free detection of analytes. Furthermore, these proteins are easy to produce, form pores with defined sizes, and can be easily manipulated with standard molecular biology techniques. The range of possible analytes can be extended by using externally added adapter molecules. Here, we provide an overview of current nanopore applications with a focus on engineering strategies and solutions.
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22
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Sathyanarayana P, Visweswariah SS, Ayappa KG. Mechanistic Insights into Pore Formation by an α-Pore Forming Toxin: Protein and Lipid Bilayer Interactions of Cytolysin A. Acc Chem Res 2021; 54:120-131. [PMID: 33291882 DOI: 10.1021/acs.accounts.0c00551] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Pore forming toxins (PFTs) are the largest class of bacterial toxins playing a central role in bacterial pathogenesis. They are proteins specifically designed to form nanochannels in the membranes of target cells, ultimately resulting in cell death and establishing infection. PFTs are broadly classified as α- and β-PFTs, depending on secondary structures that form the transmembrane channel. A unique feature about this class of proteins is the drastic conformational changes and complex oligomerization pathways that occur upon exposure to the plasma membrane. A molecular understanding of pore formation has implications in designing novel intervention strategies to combat rising antimicrobial resistance, targeted-cancer therapy, as well as designing nanopores for specialized technologies. Central to unraveling the pore formation pathway is the availability of high resolution crystal structures. In this regard, β-toxins are better understood, when compared with α-toxins whose pore forming mechanisms are complicated by an incomplete knowledge of the driving forces for amphiphatic membrane-inserted helices to organize into functional pores. With the publication of the first crystal structure for an α-toxin, cytolysin A (ClyA), in 2009 we embarked on an extensive multiscale study to unravel its pore forming mechanism. This Account represents the collective mechanistic knowledge gained in our laboratories using a variety of experimental and theoretical techniques which include large scale molecular dynamics (MD) simulations, kinetic modeling studies, single-molecule fluorescence imaging, and super-resolution spectroscopy. We reported MD simulations of the ClyA protomer, oligomeric intermediates, and full pore complex in a lipid bilayer and mapped the conformational transitions that accompany membrane binding. Using single-molecule fluorescence imaging, the conformational transition was experimentally verified by analysis of various diffusion states of membrane bound ClyA. Importantly, we have uncovered a hitherto unknown putative cholesterol binding motif in the membrane-inserted helix of ClyA. Distinct binding pockets for cholesterol formed by adjacent membrane-inserted helices are revealed in MD simulations. Cholesterol appears to play a dual role by stabilizing both the membrane-inserted protomer as well as oligomeric intermediates. Molecular dynamics simulations and kinetic modeling studies suggest that the membrane-inserted arcs oligomerize reversibly to form the predominant transmembrane oligomeric intermediates during pore formation. We posit that this mechanistic understanding of the complex action of α-PFTs has implications in unraveling pore assembly across the wider family of bacterial toxins. With emerging antimicrobial resistance, alternate therapies may rely on disrupting pore functionality or oligomerization of these pathogenic determinants utilized by bacteria, and our study includes assessing the potential for dendrimers as pore blockers.
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Affiliation(s)
- Pradeep Sathyanarayana
- Centre for BioSystems Science and Engineering, Indian Institute of Science, Bangalore, India 560012
| | - Sandhya S. Visweswariah
- Centre for BioSystems Science and Engineering, Indian Institute of Science, Bangalore, India 560012
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India 560012
| | - K. Ganapathy Ayappa
- Centre for BioSystems Science and Engineering, Indian Institute of Science, Bangalore, India 560012
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, India 560012
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Characteristics of the Protein Complexes and Pores Formed by Bacillus cereus Hemolysin BL. Toxins (Basel) 2020; 12:toxins12110672. [PMID: 33114414 PMCID: PMC7694065 DOI: 10.3390/toxins12110672] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 10/13/2020] [Accepted: 10/21/2020] [Indexed: 11/25/2022] Open
Abstract
Bacillus cereus Hemolysin BL is a tripartite toxin responsible for a diarrheal type of food poisoning. Open questions remain regarding its mode of action, including the extent to which complex formation prior to cell binding contributes to pore-forming activity, how these complexes are composed, and the properties of the pores formed in the target cell membrane. Distinct complexes of up to 600 kDa were found on native gels, whose structure and size were primarily defined by Hbl B. Hbl L1 and L2 were also identified in these complexes using Western blotting and an LC-MS approach. LC-MS also revealed that many other proteins secreted by B. cereus exist in complexes. Further, a decrease of toxic activity at temperatures ≥60 °C was shown, which was unexpectedly restored at higher temperatures. This could be attributed to a release of Hbl B monomers from tight complexation, resulting in enhanced cell binding. In contrast, Hbl L1 was rather susceptible to heat, while heat treatment of Hbl L2 seemed not to be crucial. Furthermore, Hbl-induced pores had a rather small single-channel conductance of around 200 pS and a probable channel diameter of at least 1 nm on planar lipid bilayers. These were highly instable and had a limited lifetime, and were also slightly cation-selective. Altogether, this study provides astonishing new insights into the complex mechanism of Hbl pore formation, as well as the properties of the pores.
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Peng W, de Souza Santos M, Li Y, Tomchick DR, Orth K. High-resolution cryo-EM structures of the E. coli hemolysin ClyA oligomers. PLoS One 2019; 14:e0213423. [PMID: 31048915 PMCID: PMC6497250 DOI: 10.1371/journal.pone.0213423] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 04/08/2019] [Indexed: 11/29/2022] Open
Abstract
Pore-forming proteins (PFPs) represent a functionally important protein family, that are found in organisms from viruses to humans. As a major branch of PFPs, bacteria pore-forming toxins (PFTs) permeabilize membranes and usually cause the death of target cells. E. coli hemolysin ClyA is the first member with the pore complex structure solved among α-PFTs, employing α-helices as transmembrane elements. ClyA is proposed to form pores composed of various numbers of protomers. With high-resolution cryo-EM structures, we observe that ClyA pore complexes can exist as newly confirmed oligomers of a tridecamer and a tetradecamer, at estimated resolutions of 3.2 Å and 4.3 Å, respectively. The 2.8 Å cryo-EM structure of a dodecamer dramatically improves the existing structural model. Structural analysis indicates that protomers from distinct oligomers resemble each other and neighboring protomers adopt a conserved interaction mode. We also show a stabilized intermediate state of ClyA during the transition process from soluble monomers to pore complexes. Unexpectedly, even without the formation of mature pore complexes, ClyA can permeabilize membranes and allow leakage of particles less than ~400 Daltons. In addition, we are the first to show that ClyA forms pore complexes in the presence of cholesterol within artificial liposomes. These findings provide new mechanistic insights into the dynamic process of pore assembly for the prototypical α-PFT ClyA.
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Affiliation(s)
- Wei Peng
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
| | - Marcela de Souza Santos
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
| | - Yang Li
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
| | - Diana R Tomchick
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
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25
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Dingfelder F, Benke S, Nettels D, Schuler B. Mapping an Equilibrium Folding Intermediate of the Cytolytic Pore Toxin ClyA with Single-Molecule FRET. J Phys Chem B 2018; 122:11251-11261. [PMID: 30156409 DOI: 10.1021/acs.jpcb.8b07026] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The 303-residue cytolytic toxin ClyA forms a stable α-helical monomer. In the presence of detergents or membranes, however, the protein makes a large conformational transition to the protomer state, which is competent for assembly into a dodecameric cytolytic pore. In this study, we map the structure of the ClyA monomer during denaturant-induced unfolding with single-molecule Förster resonance energy transfer (FRET) spectroscopy. To this end, we probe intramolecular distances of six different segments of ClyA by placing donor and acceptor fluorophores at corresponding positions along the chain. We identify an intermediate state that contains the folded core consisting of three of the α-helices that make up the helical bundle present in the structure of both the monomer and the protomer, but with the C- and N-terminal helices unfolded, in accord with the secondary structure content estimated from circular dichroism (CD) spectroscopy. The existence of this intermediate is likely to be a consequence of the structural bistability underlying the biological function of ClyA: The terminal helices are part of the largest rearrangements during protomer formation, and the local differences in stability we detect may prime the protein for the required conformational transition.
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Affiliation(s)
- Fabian Dingfelder
- Department of Biochemistry , University of Zurich , Winterthurerstrasse 190 , 8057 Zurich , Switzerland
| | - Stephan Benke
- Department of Biochemistry , University of Zurich , Winterthurerstrasse 190 , 8057 Zurich , Switzerland
| | - Daniel Nettels
- Department of Biochemistry , University of Zurich , Winterthurerstrasse 190 , 8057 Zurich , Switzerland
| | - Benjamin Schuler
- Department of Biochemistry , University of Zurich , Winterthurerstrasse 190 , 8057 Zurich , Switzerland.,Department of Physics , University of Zurich , Winterthurerstrasse 190 , 8057 Zurich , Switzerland
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26
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Bräuning B, Groll M. Structural and Mechanistic Features of ClyA-Like α-Pore-Forming Toxins. Toxins (Basel) 2018; 10:toxins10090343. [PMID: 30142951 PMCID: PMC6162564 DOI: 10.3390/toxins10090343] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 08/16/2018] [Accepted: 08/22/2018] [Indexed: 11/24/2022] Open
Abstract
Recent technological advances have seen increasing numbers of complex structures from diverse pore-forming toxins (PFT). The ClyA family of α-PFTs comprises a broad variety of assemblies including single-, two- and three-component toxin systems. With crystal structures available for soluble subunits of all major groups in this extended protein family, efforts now focus on obtaining molecular insights into physiological pore formation. This review provides an up-to-date discussion on common and divergent structural and functional traits that distinguish the various ClyA family PFTs. Open questions of this research topic are outlined and discussed.
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Affiliation(s)
- Bastian Bräuning
- Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
| | - Michael Groll
- Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
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27
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Cholesterol promotes Cytolysin A activity by stabilizing the intermediates during pore formation. Proc Natl Acad Sci U S A 2018; 115:E7323-E7330. [PMID: 30012608 DOI: 10.1073/pnas.1721228115] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Pore-forming toxins (PFTs) form nanoscale pores across target membranes causing cell death. Cytolysin A (ClyA) from Escherichia coli is a prototypical α-helical toxin that contributes to cytolytic phenotype of several pathogenic strains. It is produced as a monomer and, upon membrane exposure, undergoes conformational changes and finally oligomerizes to form a dodecameric pore, thereby causing ion imbalance and finally cell death. However, our current understanding of this assembly process is limited to studies in detergents, which do not capture the physicochemical properties of biological membranes. Here, using single-molecule imaging and molecular dynamics simulations, we study the ClyA assembly pathway on phospholipid bilayers. We report that cholesterol stimulates pore formation, not by enhancing initial ClyA binding to the membrane but by selectively stabilizing a protomer-like conformation. This was mediated by specific interactions by cholesterol-interacting residues in the N-terminal helix. Additionally, cholesterol stabilized the oligomeric structure using bridging interactions in the protomer-protomer interfaces, thereby resulting in enhanced ClyA oligomerization. This dual stabilization of distinct intermediates by cholesterol suggests a possible molecular mechanism by which ClyA achieves selective membrane rupture of eukaryotic cell membranes. Topological similarity to eukaryotic membrane proteins suggests evolution of a bacterial α-toxin to adopt eukaryotic motifs for its activation. Broad mechanistic correspondence between pore-forming toxins hints at a wider prevalence of similar protein membrane insertion mechanisms.
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28
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Komárek J, Ivanov Kavková E, Houser J, Horáčková A, Ždánská J, Demo G, Wimmerová M. Structure and properties of AB21, a novelAgaricus bisporusprotein with structural relation to bacterial pore-forming toxins. Proteins 2018; 86:897-911. [DOI: 10.1002/prot.25522] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 04/23/2018] [Accepted: 04/26/2018] [Indexed: 12/13/2022]
Affiliation(s)
- Jan Komárek
- Central European Institute of Technology, Masaryk University, Kamenice 5; Brno 62500 Czech Republic
- National Centre for Biomolecular Research; Faculty of Science, Masaryk University, Kotlarska 2; Brno 61137 Czech Republic
| | - Eva Ivanov Kavková
- Department of Biochemistry; Faculty of Science, Masaryk University, Kotlarska 2; Brno 61137 Czech Republic
| | - Josef Houser
- Central European Institute of Technology, Masaryk University, Kamenice 5; Brno 62500 Czech Republic
- National Centre for Biomolecular Research; Faculty of Science, Masaryk University, Kotlarska 2; Brno 61137 Czech Republic
| | - Aneta Horáčková
- Department of Biochemistry; Faculty of Science, Masaryk University, Kotlarska 2; Brno 61137 Czech Republic
| | - Jitka Ždánská
- Central European Institute of Technology, Masaryk University, Kamenice 5; Brno 62500 Czech Republic
| | - Gabriel Demo
- Central European Institute of Technology, Masaryk University, Kamenice 5; Brno 62500 Czech Republic
- National Centre for Biomolecular Research; Faculty of Science, Masaryk University, Kotlarska 2; Brno 61137 Czech Republic
| | - Michaela Wimmerová
- Central European Institute of Technology, Masaryk University, Kamenice 5; Brno 62500 Czech Republic
- National Centre for Biomolecular Research; Faculty of Science, Masaryk University, Kotlarska 2; Brno 61137 Czech Republic
- Department of Biochemistry; Faculty of Science, Masaryk University, Kotlarska 2; Brno 61137 Czech Republic
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29
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Roderer D, Glockshuber R. Assembly mechanism of the α-pore-forming toxin cytolysin A from Escherichia coli. Philos Trans R Soc Lond B Biol Sci 2018. [PMID: 28630151 DOI: 10.1098/rstb.2016.0211] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The cytolytic toxin cytolysin A (ClyA) from Escherichia coli is probably one of the best-characterized examples of bacterial, α-pore-forming toxins (α-PFTs). Like other PFTs, ClyA exists in a soluble, monomeric form that assembles to an annular, homo-oligomeric pore complex upon contact with detergent or target membranes. Comparison of the three-dimensional structures of the 34 kDa monomer and the protomer in the context of the dodecameric pore complex revealed that ClyA undergoes one of the largest conformational transitions described for proteins so far, in which 55% of the residues change their position and 16% of the residues adopt a different secondary structure in the protomer. Studies on the assembly of ClyA revealed a unique mechanism that differs from the assembly mechanism of other PFTs. The rate-liming step of pore formation proved to be the unimolecular conversion of the monomer to an assembly-competent protomer, during which a molten globule-like off-pathway intermediate accumulates. The oligomerization of protomers to pore complexes is fast and follows a kinetic scheme in which mixtures of linear oligomers of different size are formed first, followed by very rapid and specific association of pairs of oligomers that can directly perform ring closure to the dodecameric pore complex.This article is part of the themed issue 'Membrane pores: from structure and assembly, to medicine and technology'.
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Affiliation(s)
- Daniel Roderer
- Institute of Molecular Biology and Biophysics, ETH Zurich, Otto-Stern-Weg 5, 8093 Zurich, Switzerland
| | - Rudi Glockshuber
- Institute of Molecular Biology and Biophysics, ETH Zurich, Otto-Stern-Weg 5, 8093 Zurich, Switzerland
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30
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Fahie MA, Liang L, Avelino AR, Pham B, Limpikirati P, Vachet RW, Chen M. Disruption of the open conductance in the β-tongue mutants of Cytolysin A. Sci Rep 2018; 8:3796. [PMID: 29491391 PMCID: PMC5830503 DOI: 10.1038/s41598-018-22009-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 02/14/2018] [Indexed: 12/20/2022] Open
Abstract
Cytolysin A (ClyA) is a water-soluble alpha pore-forming toxin that assembles to form an oligomeric pore on host cell membranes. The ClyA monomer possesses an α-helical bundle with a β-sheet subdomain (the β-tongue) previously believed to be critical for pore assembly and/or insertion. Oligomerization of ClyA pores transforms the β-tongue into a helix-turn-helix that embeds into the lipid bilayer. Here, we show that mutations of the β-tongue did not prevent oligomerization or transmembrane insertion. Instead, β-tongue substitution mutants yielded pores with decreased conductance while a deletion mutation resulted in pores that rapidly closed following membrane association. Our results suggest that the β-tongue may play an essential structural role in stabilizing the open conformation of the transmembrane domain.
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Affiliation(s)
- Monifa A Fahie
- Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, MA, 01003, USA.,Department of Chemistry, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Lucas Liang
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Alzira R Avelino
- Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Bach Pham
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | | | - Richard W Vachet
- Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, MA, 01003, USA.,Department of Chemistry, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Min Chen
- Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, MA, 01003, USA. .,Department of Chemistry, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
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31
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Sarangi NK, Basu JK. Pathways for creation and annihilation of nanoscale biomembrane domains reveal alpha and beta-toxin nanopore formation processes. Phys Chem Chem Phys 2018; 20:29116-29130. [DOI: 10.1039/c8cp05729j] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Raft-like functional domains with putative sizes of 20–200 nm and which are evolving dynamically are believed to be the most crucial regions in cellular membranes which determine cell signaling and various functions of cells.
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Affiliation(s)
| | - Jaydeep Kumar Basu
- Department of Physics
- Indian Institute of Science
- Bangalore – 560 012
- India
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32
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Desikan R, Maiti PK, Ayappa KG. Assessing the Structure and Stability of Transmembrane Oligomeric Intermediates of an α-Helical Toxin. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:11496-11510. [PMID: 28930630 DOI: 10.1021/acs.langmuir.7b02277] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Protein membrane interactions play an important role in our understanding of diverse phenomena ranging from membrane-assisted protein aggregation to oligomerization and folding. Pore-forming toxins (PFTs) are the primary vehicle for infection by several strains of bacteria. These proteins which are expressed in a water-soluble form (monomers) bind to the target membrane and conformationally transform (protomers) and self-assemble to form a multimer transmembrane pore complex through a process of oligomerization. On the basis of the structure of the transmembrane domains, PFTs are broadly classified into β or α toxins. In contrast to β-PFTs, the paucity of available crystal structures coupled with the amphipathic nature of the transmembrane domains has hindered our understanding of α-PFT pore formation. In this article, we use molecular dynamics (MD) simulations to examine the process of pore formation of the bacterial α-PFT, cytolysin A from Escherichia coli (ClyA) in lipid bilayer membranes. Using atomistic MD simulations ranging from 50 to 500 ns, we show that transmembrane oligomeric intermediates or "arcs" form stable proteolipidic complexes consisting of protein arcs with toroidal lipids lining the free edges. By creating initial conditions where the lipids are contained within the arcs, we study the dynamics of spontaneous lipid evacuation and toroidal edge formation. This process occurs on the time scale of tens of nanoseconds, suggesting that once protomers oligomerize, transmembrane arcs are rapidly stabilized to form functional water channels capable of leakage. Using umbrella sampling with a coarse-grained molecular model, we obtain the free energy of insertion of a single protomer into the membrane. A single inserted protomer has a stabilization free energy of -52.9 ± 1.2 kJ/mol and forms a stable transmembrane water channel capable of leakage. Our simulations reveal that arcs are stable and viable intermediates that can occur during the pore-formation pathway for ClyA.
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Affiliation(s)
- Rajat Desikan
- Department of Chemical Engineering, ‡Centre for Condensed Matter Theory, Department of Physics, and §Centre for Biosystems Science and Engineering, Indian Institute of Science , Bengaluru, India 560012
| | - Prabal K Maiti
- Department of Chemical Engineering, ‡Centre for Condensed Matter Theory, Department of Physics, and §Centre for Biosystems Science and Engineering, Indian Institute of Science , Bengaluru, India 560012
| | - K Ganapathy Ayappa
- Department of Chemical Engineering, ‡Centre for Condensed Matter Theory, Department of Physics, and §Centre for Biosystems Science and Engineering, Indian Institute of Science , Bengaluru, India 560012
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33
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Desikan R, Patra SM, Sarthak K, Maiti PK, Ayappa KG. Comparison of coarse-grained (MARTINI) and atomistic molecular dynamics simulations of $$\alpha $$ α and $$\beta $$ β toxin nanopores in lipid membranes. J CHEM SCI 2017. [DOI: 10.1007/s12039-017-1316-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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34
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Fortea E, Lemieux V, Potvin L, Chikwana V, Griffin S, Hey T, McCaskill D, Narva K, Tan SY, Xu X, Vachon V, Schwartz JL. Cry6Aa1, a Bacillus thuringiensis nematocidal and insecticidal toxin, forms pores in planar lipid bilayers at extremely low concentrations and without the need of proteolytic processing. J Biol Chem 2017. [PMID: 28623231 DOI: 10.1074/jbc.m116.765941] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cry6Aa1 is a Bacillus thuringiensis (Bt) toxin active against nematodes and corn rootworm insects. Its 3D molecular structure, which has been recently elucidated, is unique among those known for other Bt toxins. Typical three-domain Bt toxins permeabilize receptor-free planar lipid bilayers (PLBs) by forming pores at doses in the 1-50 μg/ml range. Solubilization and proteolytic activation are necessary steps for PLB permeabilization. In contrast to other Bt toxins, Cry6Aa1 formed pores in receptor-free bilayers at doses as low as 200 pg/ml in a wide range of pH (5.5-9.5) and without the need of protease treatment. When Cry6Aa1 was preincubated with Western corn rootworm (WCRW) midgut juice or trypsin, 100 fg/ml of the toxin was sufficient to form pores in PLBs. The overall biophysical properties of the pores were similar for all three forms of the toxin (native, midgut juice- and trypsin-treated), with conductances ranging from 28 to 689 pS, except for their ionic selectivity, which was slightly cationic for the native and midgut juice-treated Cry6Aa1, whereas dual selectivity (to cations or anions) was observed for the pores formed by the trypsin-treated toxin. Enrichment of PLBs with WCRW midgut brush-border membrane material resulted in a 2000-fold reduction of the amount of native Cry6Aa1 required to form pores and affected the biophysical properties of both the native and trypsin-treated forms of the toxin. These results indicate that, although Cry6Aa1 forms pores, the molecular determinants of its mode of action are significantly different from those reported for other Bt toxins.
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Affiliation(s)
- Eva Fortea
- From the Département de pharmacologie et physiologie and Groupe d'étude des protéines membranaires, Université de Montréal, Montreal, Québec H3C 3J7, Canada
| | - Vincent Lemieux
- From the Département de pharmacologie et physiologie and Groupe d'étude des protéines membranaires, Université de Montréal, Montreal, Québec H3C 3J7, Canada.,the Département de biologie, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
| | - Léna Potvin
- From the Département de pharmacologie et physiologie and Groupe d'étude des protéines membranaires, Université de Montréal, Montreal, Québec H3C 3J7, Canada
| | | | | | - Timothy Hey
- Dow AgroSciences LLC, Indianapolis, Indiana 46268, and
| | | | - Kenneth Narva
- Dow AgroSciences LLC, Indianapolis, Indiana 46268, and
| | - Sek Yee Tan
- Dow AgroSciences LLC, Indianapolis, Indiana 46268, and
| | - Xiaoping Xu
- Dow AgroSciences LLC, Indianapolis, Indiana 46268, and
| | - Vincent Vachon
- From the Département de pharmacologie et physiologie and Groupe d'étude des protéines membranaires, Université de Montréal, Montreal, Québec H3C 3J7, Canada
| | - Jean-Louis Schwartz
- From the Département de pharmacologie et physiologie and Groupe d'étude des protéines membranaires, Université de Montréal, Montreal, Québec H3C 3J7, Canada, .,the Centre SÈVE de recherche en sciences du végétal, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1 Canada
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35
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Agrawal A, Apoorva K, Ayappa KG. Transmembrane oligomeric intermediates of pore forming toxin Cytolysin A determine leakage kinetics. RSC Adv 2017. [DOI: 10.1039/c7ra07304f] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Leakage kinetics of Cytolysin A, an α pore forming toxin, occurs through stochastic insertion of oligomeric intermediates or ‘arcs’.
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Affiliation(s)
- Ayush Agrawal
- Department of Chemical Engineering
- Indian Institute of Science
- Bangalore-560012
- India
| | - K. Apoorva
- Department of Chemical Engineering
- Indian Institute of Technology
- Hyderabad-502205
- India
| | - K. G. Ayappa
- Department of Chemical Engineering
- Indian Institute of Science
- Bangalore-560012
- India
- Centre for Biosystems Science and Engineering
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36
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Hakamada K, Watanabe H, Kawano R, Noguchi K, Yohda M. Expression and characterization of the Plasmodium translocon of the exported proteins component EXP2. Biochem Biophys Res Commun 2017; 482:700-705. [DOI: 10.1016/j.bbrc.2016.11.097] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 11/16/2016] [Indexed: 10/20/2022]
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37
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Giri Rao VVH, Desikan R, Ayappa KG, Gosavi S. Capturing the Membrane-Triggered Conformational Transition of an α-Helical Pore-Forming Toxin. J Phys Chem B 2016; 120:12064-12078. [DOI: 10.1021/acs.jpcb.6b09400] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- V. V. Hemanth Giri Rao
- Simons
Centre for the Study of Living Machines, National Centre for Biological
Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India
| | - Rajat Desikan
- Department
of Chemical Engineering, Indian Institute of Science, Bengaluru 560012, India
| | - K. Ganapathy Ayappa
- Department
of Chemical Engineering, Indian Institute of Science, Bengaluru 560012, India
- Centre
for Biosystems Science and Engineering, Indian Institute of Science, Bengaluru 560012, India
| | - Shachi Gosavi
- Simons
Centre for the Study of Living Machines, National Centre for Biological
Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India
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38
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Didier A, Dietrich R, Märtlbauer E. Antibody Binding Studies Reveal Conformational Flexibility of the Bacillus cereus Non-Hemolytic Enterotoxin (Nhe) A-Component. PLoS One 2016; 11:e0165135. [PMID: 27768742 PMCID: PMC5074587 DOI: 10.1371/journal.pone.0165135] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 10/06/2016] [Indexed: 11/18/2022] Open
Abstract
The non-hemolytic enterotoxin complex (Nhe) is supposed to be the main virulence factor of B. cereus causing a diarrheal outcome of food poisoning. This tripartite toxin consists of the single components NheA, -B and -C all of them being necessary for maximum toxicity. In the past, research activities aiming to elucidate the mode-of-action of Nhe were mostly focused on the B- and C-component. In this study the generation of novel monoclonal antibodies (mAb) and their thorough characterization enabled the determination of key features for NheA. By the means of immunoaffinity chromatography it could be shown that NheA does not interact with -B and -C in solution. Additionally, the establishment of a highly sensitive sandwich-EIA now enables the detection of NheA in B. cereus supernatants down to 20 pg ml-1.Peptide-based epitope mapping in combination with partially deleted recombinant NheA fragments allowed the allocation of the binding regions for the three mAbs under study. Furthermore, by different EIA set-ups the conformational flexibility of NheA could be shown. For two of the antibodies under study different mechanisms of NheA neutralization were proven. Due to prevention of complete pore formation by one of the antibodies, NheA could be detected in an intermediate stage of the tripartite complex on the cell surface. Taken together, the results obtained in the present study allow a refinement of the mode-of-action for the Nhe toxin-complex.
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Affiliation(s)
- A. Didier
- Department of Veterinary Science, Ludwig-Maximilians Universität München, Oberschleißheim, Germany
- * E-mail:
| | - R. Dietrich
- Department of Veterinary Science, Ludwig-Maximilians Universität München, Oberschleißheim, Germany
| | - E. Märtlbauer
- Department of Veterinary Science, Ludwig-Maximilians Universität München, Oberschleißheim, Germany
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39
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Sathyanarayana P, Desikan R, Ayappa KG, Visweswariah SS. The Solvent-Exposed C-Terminus of the Cytolysin A Pore-Forming Toxin Directs Pore Formation and Channel Function in Membranes. Biochemistry 2016; 55:5952-5961. [DOI: 10.1021/acs.biochem.6b00593] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Pradeep Sathyanarayana
- Centre
for Biosystems Science and Engineering, ‡Department of Chemical Engineering, and §Department of
Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore 560012, India
| | - Rajat Desikan
- Centre
for Biosystems Science and Engineering, ‡Department of Chemical Engineering, and §Department of
Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore 560012, India
| | - K. Ganapathy Ayappa
- Centre
for Biosystems Science and Engineering, ‡Department of Chemical Engineering, and §Department of
Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore 560012, India
| | - Sandhya S. Visweswariah
- Centre
for Biosystems Science and Engineering, ‡Department of Chemical Engineering, and §Department of
Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore 560012, India
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40
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Huang J, Guan Z, Wan L, Zou T, Sun M. Crystal structure of Cry6Aa: A novel nematicidal ClyA-type α-pore-forming toxin from Bacillus thuringiensis. Biochem Biophys Res Commun 2016; 478:307-313. [DOI: 10.1016/j.bbrc.2016.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2016] [Accepted: 07/01/2016] [Indexed: 01/30/2023]
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41
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Dementiev A, Board J, Sitaram A, Hey T, Kelker MS, Xu X, Hu Y, Vidal-Quist C, Chikwana V, Griffin S, McCaskill D, Wang NX, Hung SC, Chan MK, Lee MM, Hughes J, Wegener A, Aroian RV, Narva KE, Berry C. The pesticidal Cry6Aa toxin from Bacillus thuringiensis is structurally similar to HlyE-family alpha pore-forming toxins. BMC Biol 2016; 14:71. [PMID: 27576487 PMCID: PMC5004264 DOI: 10.1186/s12915-016-0295-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 08/10/2016] [Indexed: 12/02/2022] Open
Abstract
Background The Cry6 family of proteins from Bacillus thuringiensis represents a group of powerful toxins with great potential for use in the control of coleopteran insects and of nematode parasites of importance to agriculture. These proteins are unrelated to other insecticidal toxins at the level of their primary sequences and the structure and function of these proteins has been poorly studied to date. This has inhibited our understanding of these toxins and their mode of action, along with our ability to manipulate the proteins to alter their activity to our advantage. To increase our understanding of their mode of action and to facilitate further development of these proteins we have determined the structure of Cry6Aa in protoxin and trypsin-activated forms and demonstrated a pore-forming mechanism of action. Results The two forms of the toxin were resolved to 2.7 Å and 2.0 Å respectively and showed very similar structures. Cry6Aa shows structural homology to a known class of pore-forming toxins including hemolysin E from Escherichia coli and two Bacillus cereus proteins: the hemolytic toxin HblB and the NheA component of the non-hemolytic toxin (pfam05791). Cry6Aa also shows atypical features compared to other members of this family, including internal repeat sequences and small loop regions within major alpha helices. Trypsin processing was found to result in the loss of some internal sequences while the C-terminal region remains disulfide-linked to the main core of the toxin. Based on the structural similarity of Cry6Aa to other toxins, the mechanism of action of the toxin was probed and its ability to form pores in vivo in Caenorhabditis elegans was demonstrated. A non-toxic mutant was also produced, consistent with the proposed pore-forming mode of action. Conclusions Cry6 proteins are members of the alpha helical pore-forming toxins – a structural class not previously recognized among the Cry toxins of B. thuringiensis and representing a new paradigm for nematocidal and insecticidal proteins. Elucidation of both the structure and the pore-forming mechanism of action of Cry6Aa now opens the way to more detailed analysis of toxin specificity and the development of new toxin variants with novel activities. Electronic supplementary material The online version of this article (doi:10.1186/s12915-016-0295-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Jason Board
- Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff, CF15 8FA, UK
| | - Anand Sitaram
- University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA, 01605-2377, USA
| | - Timothy Hey
- Dow AgroSciences, LLC, Indianapolis, IN, USA.,Present address: Indiana State Department of Health Laboratories, Indianapolis, IN, USA
| | - Matthew S Kelker
- Dow AgroSciences, LLC, Indianapolis, IN, USA.,Present address: Xylogenics, LLC, Indianapolis, IN, USA
| | - Xiaoping Xu
- Dow AgroSciences, LLC, Indianapolis, IN, USA
| | - Yan Hu
- University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA, 01605-2377, USA
| | - Cristian Vidal-Quist
- Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff, CF15 8FA, UK.,Present address: Laboratorio de Interacción Planta-Insecto, Departamento de Biología Medioambiental, Centro de Investigaciones Biológicas - CSIC, Madrid, Spain
| | | | | | | | - Nick X Wang
- Dow AgroSciences, LLC, Indianapolis, IN, USA
| | | | - Michael K Chan
- School of Life Sciences and Center of Novel Biomaterials, The Chinese University of Hong Kong, Shatin, HK SAR, China
| | - Marianne M Lee
- School of Life Sciences and Center of Novel Biomaterials, The Chinese University of Hong Kong, Shatin, HK SAR, China
| | - Jessica Hughes
- Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff, CF15 8FA, UK.,Present address: Antimicrobial Reference Laboratory, Southmead Hospital, Westbury-on-Trym, Bristol, BS10 5NB, UK
| | - Alice Wegener
- Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff, CF15 8FA, UK
| | - Raffi V Aroian
- University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA, 01605-2377, USA
| | | | - Colin Berry
- Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff, CF15 8FA, UK.
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42
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Morante K, Bellomio A, Gil-Cartón D, Redondo-Morata L, Sot J, Scheuring S, Valle M, González-Mañas JM, Tsumoto K, Caaveiro JMM. Identification of a Membrane-bound Prepore Species Clarifies the Lytic Mechanism of Actinoporins. J Biol Chem 2016; 291:19210-19219. [PMID: 27445331 PMCID: PMC5016661 DOI: 10.1074/jbc.m116.734053] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Indexed: 11/06/2022] Open
Abstract
Pore-forming toxins (PFTs) are cytolytic proteins belonging to the molecular warfare apparatus of living organisms. The assembly of the functional transmembrane pore requires several intermediate steps ranging from a water-soluble monomeric species to the multimeric ensemble inserted in the cell membrane. The non-lytic oligomeric intermediate known as prepore plays an essential role in the mechanism of insertion of the class of β-PFTs. However, in the class of α-PFTs, like the actinoporins produced by sea anemones, evidence of membrane-bound prepores is still lacking. We have employed single-particle cryo-electron microscopy (cryo-EM) and atomic force microscopy to identify, for the first time, a prepore species of the actinoporin fragaceatoxin C bound to lipid vesicles. The size of the prepore coincides with that of the functional pore, except for the transmembrane region, which is absent in the prepore. Biochemical assays indicated that, in the prepore species, the N terminus is not inserted in the bilayer but is exposed to the aqueous solution. Our study reveals the structure of the prepore in actinoporins and highlights the role of structural intermediates for the formation of cytolytic pores by an α-PFT.
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Affiliation(s)
- Koldo Morante
- From the Department of Bioengineering, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.,the Department of Biochemistry and Molecular Biology and.,Biofisika Institute (UPV/EHU, CSIC), University of the Basque Country, P. O. Box 644, 48080 Bilbao, Spain
| | - Augusto Bellomio
- the Department of Biochemistry and Molecular Biology and.,Biofisika Institute (UPV/EHU, CSIC), University of the Basque Country, P. O. Box 644, 48080 Bilbao, Spain
| | - David Gil-Cartón
- the Structural Biology Unit, Center for Cooperative Research in Biosciences, CICbiogune, 48160 Derio, Spain
| | - Lorena Redondo-Morata
- the U1006 INSERM, Aix-Marseille Université, Parc Scientifique et Technologique de Luminy, 163 Avenue de Luminy, 13009 Marseille, France, and
| | - Jesús Sot
- the Department of Biochemistry and Molecular Biology and.,Biofisika Institute (UPV/EHU, CSIC), University of the Basque Country, P. O. Box 644, 48080 Bilbao, Spain
| | - Simon Scheuring
- the U1006 INSERM, Aix-Marseille Université, Parc Scientifique et Technologique de Luminy, 163 Avenue de Luminy, 13009 Marseille, France, and
| | - Mikel Valle
- the Structural Biology Unit, Center for Cooperative Research in Biosciences, CICbiogune, 48160 Derio, Spain
| | | | - Kouhei Tsumoto
- From the Department of Bioengineering, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan, .,the Institute of Medical Science, University of Tokyo, Minato-ku, 108-8639 Tokyo, Japan
| | - Jose M M Caaveiro
- From the Department of Bioengineering, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan,
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43
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Roderer D, Benke S, Schuler B, Glockshuber R. Soluble Oligomers of the Pore-forming Toxin Cytolysin A from Escherichia coli Are Off-pathway Products of Pore Assembly. J Biol Chem 2016; 291:5652-5663. [PMID: 26757820 DOI: 10.1074/jbc.m115.700757] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Indexed: 11/06/2022] Open
Abstract
The α-pore-forming toxin Cytolysin A (ClyA) is responsible for the hemolytic activity of various Escherichia coli and Salmonella enterica strains. Soluble ClyA monomers spontaneously assemble into annular dodecameric pore complexes upon contact with membranes or detergent. At ClyA monomer concentrations above ∼100 nm, the rate-limiting step in detergent- or membrane- induced pore assembly is the unimolecular reaction from the monomer to the assembly-competent protomer, which then oligomerizes rapidly to active pore complexes. In the absence of detergent, ClyA slowly forms soluble oligomers. Here we show that soluble ClyA oligomers cannot form dodecameric pore complexes after the addition of detergent and are hemolytically inactive. In addition, we demonstrate that the natural cysteine pair Cys-87/Cys-285 of ClyA forms a disulfide bond under oxidizing conditions and that both the oxidized and reduced ClyA monomers assemble to active pores via the same pathway in the presence of detergent, in which an unstructured, monomeric intermediate is transiently populated. The results show that the oxidized ClyA monomer assembles to pore complexes about one order of magnitude faster than the reduced monomer because the unstructured intermediate of oxidized ClyA is less stable and dissolves more rapidly than the reduced intermediate. Moreover, we show that oxidized ClyA forms soluble, inactive oligomers in the absence of detergent much faster than the reduced monomer, providing an explanation for several contradictory reports in which oxidized ClyA had been described as inactive.
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Affiliation(s)
- Daniel Roderer
- From the Institute of Molecular Biology and Biophysics ETH Zurich, Otto-Stern-Weg 5, CH-8093 Zurich, Switzerland and.
| | - Stephan Benke
- the Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Benjamin Schuler
- the Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Rudi Glockshuber
- From the Institute of Molecular Biology and Biophysics ETH Zurich, Otto-Stern-Weg 5, CH-8093 Zurich, Switzerland and
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44
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Formation of small transmembrane pores: An intermediate stage on the way to Bacillus cereus non-hemolytic enterotoxin (Nhe) full pores in the absence of NheA. Biochem Biophys Res Commun 2015; 469:613-8. [PMID: 26654951 DOI: 10.1016/j.bbrc.2015.11.126] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 11/27/2015] [Indexed: 02/03/2023]
Abstract
The non-hemolytic enterotoxin (Nhe) of Bacillus cereus is a three-partite toxin formed of the components NheA, -B and -C. Pore formation and subsequent lysis of target cells caused by Nhe is an orchestrated process comprising three steps: (i) formation of NheB/C oligomers in solution, (ii) attachment of the oligomers to the cell membrane, (iii) binding of NheA to the oligomers. The present study aimed to characterize the properties of the NheB/C complex and the fate of the target cell upon binding. An enzyme immunoassay allowing kinetic measurements and surface plasmon resonance revealed the fast and high affinity formation of the NheB/C oligomers. The benefit of these complexes is a more stable cell binding as well as stronger and earlier cytotoxic effect. High molecular mass hetero-oligomers (620 kDa) probably consisting of one NheC and up to 15 NheB were detected by size-exclusion chromatography and on native PAGE immunoblots. Due to the NheBC application the morphology and membrane permeability of Vero cells is partly disturbed. Formation of stable transmembrane channels with a conductance of about 870 pS and a diameter of about 2 nm due to the application of NheBC could be demonstrated in lipid bilayer experiments. Thus, the NheBC complex itself has a tendency to increase the membrane permeability prior to the emergence of full pores containing also NheA.
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45
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Assemblies of pore-forming toxins visualized by atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:500-11. [PMID: 26577274 DOI: 10.1016/j.bbamem.2015.11.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Revised: 10/23/2015] [Accepted: 11/09/2015] [Indexed: 02/05/2023]
Abstract
A number of pore-forming toxins (PFTs) can assemble on lipid membranes through their specific interactions with lipids. The oligomeric assemblies of some PFTs have been successfully revealed either by electron microscopy (EM) and/or atomic force microscopy (AFM). Unlike EM, AFM imaging can be performed under physiological conditions, enabling the real-time visualization of PFT assembly and the transition from the prepore state, in which the toxin does not span the membrane, to the pore state. In addition to characterizing PFT oligomers, AFM has also been used to examine toxin-induced alterations in membrane organization. In this review, we summarize the contributions of AFM to the understanding of both PFT assembly and PFT-induced membrane reorganization. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.
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46
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Cosentino K, Ros U, García-Sáez AJ. Assembling the puzzle: Oligomerization of α-pore forming proteins in membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:457-466. [PMID: 26375417 DOI: 10.1016/j.bbamem.2015.09.013] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/26/2015] [Accepted: 09/09/2015] [Indexed: 12/21/2022]
Abstract
Pore forming proteins (PFPs) share the ability of creating pores that allow the passage of ions, proteins or other constituents through a wide variety of target membranes, ranging from bacteria to humans. They often cause cell death, as pore formation disrupts the membrane permeability barrier required for maintaining cell homeostasis. The organization into supramolecular complexes or oligomers that pierce the membrane is a common feature of PFPs. However, the molecular pathway of self-assembly and pore opening remains unclear. Here, we review the most recent discoveries in the mechanism of membrane oligomerization and pore formation of a subset of PFPs, the α-PFPs, whose pore-forming domains are formed by helical segments. Only now we are starting to grasp the molecular details of their function, mainly thanks to the introduction of single molecule microscopy and nanoscopy techniques. This article is part of a Special Issue entitled: Pore-forming toxins edited by Mauro Dalla Serra and Franco Gambale.
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Affiliation(s)
- Katia Cosentino
- Interfaculty Institute of Biochemistry (IFIB), University of Tübingen, Tübingen, Germany.,Max-Planck Institute for Intelligent Systems, Stuttgart, Germany
| | - Uris Ros
- Interfaculty Institute of Biochemistry (IFIB), University of Tübingen, Tübingen, Germany.,Max-Planck Institute for Intelligent Systems, Stuttgart, Germany.,Center for Protein Studies, Havana University, Havana, Cuba
| | - Ana J García-Sáez
- Interfaculty Institute of Biochemistry (IFIB), University of Tübingen, Tübingen, Germany.,Max-Planck Institute for Intelligent Systems, Stuttgart, Germany
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47
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AhYoung AP, Koehl A, Cascio D, Egea PF. Structural mapping of the ClpB ATPases of Plasmodium falciparum: Targeting protein folding and secretion for antimalarial drug design. Protein Sci 2015; 24:1508-20. [PMID: 26130467 DOI: 10.1002/pro.2739] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 06/24/2015] [Accepted: 06/26/2015] [Indexed: 11/08/2022]
Abstract
Caseinolytic chaperones and proteases (Clp) belong to the AAA+ protein superfamily and are part of the protein quality control machinery in cells. The eukaryotic parasite Plasmodium falciparum, the causative agent of malaria, has evolved an elaborate network of Clp proteins including two distinct ClpB ATPases. ClpB1 and ClpB2 are involved in different aspects of parasitic proteostasis. ClpB1 is present in the apicoplast, a parasite-specific and plastid-like organelle hosting various metabolic pathways necessary for parasite growth. ClpB2 localizes to the parasitophorous vacuole membrane where it drives protein export as core subunit of a parasite-derived protein secretion complex, the Plasmodium Translocon of Exported proteins (PTEX); this process is central to parasite virulence and survival in the human host. The functional associations of these two chaperones with parasite-specific metabolism and protein secretion make them prime drug targets. ClpB proteins function as unfoldases and disaggregases and share a common architecture consisting of four domains-a variable N-terminal domain that binds different protein substrates, followed by two highly conserved catalytic ATPase domains, and a C-terminal domain. Here, we report and compare the first crystal structures of the N terminal domains of ClpB1 and ClpB2 from Plasmodium and analyze their molecular surfaces. Solution scattering analysis of the N domain of ClpB2 shows that the average solution conformation is similar to the crystalline structure. These structures represent the first step towards the characterization of these two malarial chaperones and the reconstitution of the entire PTEX to aid structure-based design of novel anti-malarial drugs.
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Affiliation(s)
- Andrew P AhYoung
- Department of Biological Chemistry, David Geffen School of Medicine, UCLA, Los Angeles, California
| | - Antoine Koehl
- Department of Biological Chemistry, David Geffen School of Medicine, UCLA, Los Angeles, California
| | - Duilio Cascio
- Department of Energy Institute for Genomics and Proteomics, UCLA, Los Angeles, California
| | - Pascal F Egea
- Department of Biological Chemistry, David Geffen School of Medicine, UCLA, Los Angeles, California.,Molecular Biology Institute, UCLA, Los Angeles, California
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48
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Tanaka K, Caaveiro JMM, Morante K, González-Mañas JM, Tsumoto K. Structural basis for self-assembly of a cytolytic pore lined by protein and lipid. Nat Commun 2015; 6:6337. [PMID: 25716479 PMCID: PMC4351601 DOI: 10.1038/ncomms7337] [Citation(s) in RCA: 166] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 01/20/2015] [Indexed: 12/12/2022] Open
Abstract
Pore-forming toxins (PFT) are water-soluble proteins that possess the remarkable ability to self-assemble on the membrane of target cells, where they form pores causing cell damage. Here, we elucidate the mechanism of action of the haemolytic protein fragaceatoxin C (FraC), a α-barrel PFT, by determining the crystal structures of FraC at four different stages of the lytic mechanism, namely the water-soluble state, the monomeric lipid-bound form, an assembly intermediate and the fully assembled transmembrane pore. The structure of the transmembrane pore exhibits a unique architecture composed of both protein and lipids, with some of the lipids lining the pore wall, acting as assembly cofactors. The pore also exhibits lateral fenestrations that expose the hydrophobic core of the membrane to the aqueous environment. The incorporation of lipids from the target membrane within the structure of the pore provides a membrane-specific trigger for the activation of a haemolytic toxin. Actinoporins are water-soluble pore-forming toxins that self-assemble in the membranes of target cells. Here, the authors provide insight into the mechanism of membrane pore formation by solving the structures of several states of the hemolytic protein fragaceatoxin C, including the fully assembled pore.
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Affiliation(s)
- Koji Tanaka
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Jose M M Caaveiro
- Department of Bioengineering, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Koldo Morante
- 1] Department of Bioengineering, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan [2] Department of Biochemistry and Molecular Biology, University of the Basque Country, Lejona, Vizcaya 48940, Spain
| | - Juan Manuel González-Mañas
- Department of Biochemistry and Molecular Biology, University of the Basque Country, Lejona, Vizcaya 48940, Spain
| | - Kouhei Tsumoto
- 1] Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan [2] Department of Bioengineering, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan [3] Laboratory of Medical Proteomics, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
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49
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Benke S, Roderer D, Wunderlich B, Nettels D, Glockshuber R, Schuler B. The assembly dynamics of the cytolytic pore toxin ClyA. Nat Commun 2015; 6:6198. [PMID: 25652783 PMCID: PMC4347018 DOI: 10.1038/ncomms7198] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 01/05/2015] [Indexed: 12/15/2022] Open
Abstract
Pore-forming toxins are protein assemblies used by many organisms to disrupt the membranes of target cells. They are expressed as soluble monomers that assemble spontaneously into multimeric pores. However, owing to their complexity, the assembly processes have not been resolved in detail for any pore-forming toxin. To determine the assembly mechanism for the ring-shaped, homododecameric pore of the bacterial cytolytic toxin ClyA, we collected a diverse set of kinetic data using single-molecule spectroscopy and complementary techniques on timescales from milliseconds to hours, and from picomolar to micromolar ClyA concentrations. The entire range of experimental results can be explained quantitatively by a surprisingly simple mechanism. First, addition of the detergent n-dodecyl-β-D-maltopyranoside to the soluble monomers triggers the formation of assembly-competent toxin subunits, accompanied by the transient formation of a molten-globule-like intermediate. Then, all sterically compatible oligomers contribute to assembly, which greatly enhances the efficiency of pore formation compared with simple monomer addition.
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Affiliation(s)
- Stephan Benke
- University of Zurich, Department of Biochemistry, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Daniel Roderer
- ETH Zurich, Institute of Molecular Biology and Biophysics, Otto-Stern-Weg 5, 8093 Zurich, Switzerland
| | - Bengt Wunderlich
- University of Zurich, Department of Biochemistry, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Daniel Nettels
- University of Zurich, Department of Biochemistry, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Rudi Glockshuber
- ETH Zurich, Institute of Molecular Biology and Biophysics, Otto-Stern-Weg 5, 8093 Zurich, Switzerland
| | - Benjamin Schuler
- University of Zurich, Department of Biochemistry, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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50
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Spillman NJ, Beck JR, Goldberg DE. Protein export into malaria parasite-infected erythrocytes: mechanisms and functional consequences. Annu Rev Biochem 2015; 84:813-41. [PMID: 25621510 DOI: 10.1146/annurev-biochem-060614-034157] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Phylum Apicomplexa comprises a large group of obligate intracellular parasites of high medical and veterinary importance. These organisms succeed intracellularly by effecting remarkable changes in a broad range of diverse host cells. The transformation of the host erythrocyte is particularly striking in the case of the malaria parasite Plasmodium falciparum. P. falciparum exports hundreds of proteins that mediate a complex cellular renovation marked by changes in the permeability, rigidity, and cytoadherence properties of the host erythrocyte. The past decade has seen enormous progress in understanding the identity and function of these exported effectors, as well as the mechanisms by which they are trafficked into the host cell. Here we review these advances, place them in the context of host manipulation by related apicomplexans, and propose key directions for future research.
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