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Chiu YC, Yeh MC, Wang CH, Chen YA, Chang H, Lin HY, Ho MC, Lin SM. Structural basis for calcium-stimulating pore formation of Vibrio α-hemolysin. Nat Commun 2023; 14:5946. [PMID: 37741869 PMCID: PMC10517994 DOI: 10.1038/s41467-023-41579-x] [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: 05/30/2023] [Accepted: 09/10/2023] [Indexed: 09/25/2023] Open
Abstract
Vibrio α-hemolysins (αHLs) are β-pore-forming toxins secreted by Vibrio pathogens, crucial for the facilitation of bacterial infections through host cell lysis. These toxins are produced as inactive precursors, requiring proteolytic maturation and membrane association for activation within host tissues. Here, we investigate Vibrio campbellii αHL (VcαHL), and establish that its hemolytic activity is significantly stimulated by calcium ions, with an EC50 that aligns with physiological calcium concentrations. Furthermore, we illustrate the vital contribution of calcium ions to the oligomerization of VcαHL on membranes. Using X-ray crystallography and cryo-electron microscopy, we decipher both the immature and assembled structures of VcαHL and elucidate the conformational changes corresponding to toxin assembly. We also identify a calcium-binding module that is integral for VcαHL's calcium-dependent activation. These findings provide insights into the regulatory mechanisms of VcαHL and have the potential to inform the development of targeted therapeutic strategies against Vibrio infections.
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Affiliation(s)
- Yu-Chuan Chiu
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan, Taiwan
| | - Min-Chi Yeh
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Chun-Hsiung Wang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Yu-An Chen
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan, Taiwan
| | - Hsiang Chang
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan, Taiwan
| | - Han-You Lin
- Department of Veterinary Medicine, School of Veterinary Medicine, National Taiwan University, Taipei, Taiwan
| | - Meng-Chiao Ho
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
- Graduate Institute of Biochemistry and Molecular Biology, National Taiwan University, Taipei, Taiwan
| | - Shih-Ming Lin
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan, Taiwan.
- Institute of Tropical Plant Sciences and Microbiology, National Cheng Kung University, Tainan, Taiwan.
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2
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Abstract
The major function of the mammalian immune system is to prevent and control infections caused by enteropathogens that collectively have altered human destiny. In fact, as the gastrointestinal tissues are the major interface of mammals with the environment, up to 70% of the human immune system is dedicated to patrolling them The defenses are multi-tiered and include the endogenous microflora that mediate colonization resistance as well as physical barriers intended to compartmentalize infections. The gastrointestinal tract and associated lymphoid tissue are also protected by sophisticated interleaved arrays of active innate and adaptive immune defenses. Remarkably, some bacterial enteropathogens have acquired an arsenal of virulence factors with which they neutralize all these formidable barriers to infection, causing disease ranging from mild self-limiting gastroenteritis to in some cases devastating human disease.
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Affiliation(s)
- Micah J. Worley
- Department of Biology, University of Louisville, Louisville, Kentucky, USA,CONTACT Micah J. Worley Department of Biology, University of Louisville, 139 Life Sciences Bldg, Louisville, Kentucky, USA
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3
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Mondal AK, Sengupta N, Singh M, Biswas R, Lata K, Lahiri I, Dutta S, Chattopadhyay K. Glu289 residue in the pore-forming motif of Vibrio cholerae cytolysin is important for efficient β-barrel pore formation. J Biol Chem 2022; 298:102441. [PMID: 36055404 PMCID: PMC9520032 DOI: 10.1016/j.jbc.2022.102441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 08/17/2022] [Accepted: 08/21/2022] [Indexed: 11/19/2022] Open
Abstract
Vibrio cholerae cytolysin (VCC) is a potent membrane-damaging β-barrel pore-forming toxin (β-PFT). Upon binding to the target membranes, VCC monomers first assemble into oligomeric pre-pore intermediates, and subsequently transform into transmembrane β-barrel pores. VCC harbors a designated pore-forming motif, which, during oligomeric pore formation, inserts into the membrane and generates a transmembrane β-barrel scaffold. It remains an enigma how the molecular architecture of the pore-forming motif regulates the VCC pore-formation mechanism. Here, we show that a specific pore-forming motif residue, E289, plays crucial regulatory roles in the pore-formation mechanism of VCC. We find that the mutation of E289A drastically compromises pore-forming activity, without affecting the structural integrity and membrane-binding potential of the toxin monomers. Although our single-particle cryo-EM analysis reveals wild type-like oligomeric β-barrel pore formation by E289A-VCC in the membrane, we demonstrate that the mutant shows severely delayed kinetics in terms of pore-forming ability that can be rescued with elevated temperature conditions. We find that the pore-formation efficacy of E289A-VCC appears to be more profoundly dependent on temperature as compared to that of the wild type toxin. Our results suggest that the E289A mutation traps membrane-bound toxin molecules in the pre-pore-like intermediate state that is hindered from converting into the functional β-barrel pores by a large energy barrier, thus highlighting the importance of this residue for the pore-formation mechanism of VCC.
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Affiliation(s)
- Anish Kumar Mondal
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Manauli, Punjab, India
| | - Nayanika Sengupta
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Mahendra Singh
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Manauli, Punjab, India
| | - Rupam Biswas
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Kusum Lata
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Manauli, Punjab, India
| | - Indrajit Lahiri
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Manauli, Punjab, India
| | - Somnath Dutta
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Kausik Chattopadhyay
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Manauli, Punjab, India.
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4
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Lata K, Singh M, Chatterjee S, Chattopadhyay K. Membrane Dynamics and Remodelling in Response to the Action of the Membrane-Damaging Pore-Forming Toxins. J Membr Biol 2022; 255:161-173. [PMID: 35305136 DOI: 10.1007/s00232-022-00227-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 03/02/2022] [Indexed: 12/11/2022]
Abstract
Pore-forming protein toxins (PFTs) represent a diverse class of membrane-damaging proteins that are produced by a wide variety of organisms. PFT-mediated membrane perforation is largely governed by the chemical composition and the physical properties of the plasma membranes. The interaction between the PFTs with the target membranes is critical for the initiation of the pore-formation process, and can lead to discrete membrane reorganization events that further aids in the process of pore-formation. Punching holes on the plasma membranes by the PFTs interferes with the cellular homeostasis by disrupting the ion-balance inside the cells that in turn can turn on multiple signalling cascades required to restore membrane integrity and cellular homeostasis. In this review, we discuss the physicochemical attributes of the plasma membranes associated with the pore-formation processes by the PFTs, and the subsequent membrane remodelling events that may start off the membrane-repair mechanisms.
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Affiliation(s)
- Kusum Lata
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, SAS Nagar, Manauli, Mohali, Punjab, 140306, India
| | - Mahendra Singh
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, SAS Nagar, Manauli, Mohali, Punjab, 140306, India
| | - Shamaita Chatterjee
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, SAS Nagar, Manauli, Mohali, Punjab, 140306, India
| | - Kausik Chattopadhyay
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, SAS Nagar, Manauli, Mohali, Punjab, 140306, India.
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5
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Singh M, Rupesh N, Pandit SB, Chattopadhyay K. Curcumin Inhibits Membrane-Damaging Pore-Forming Function of the β-Barrel Pore-Forming Toxin Vibrio cholerae Cytolysin. Front Microbiol 2022; 12:809782. [PMID: 35140698 PMCID: PMC8818996 DOI: 10.3389/fmicb.2021.809782] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 12/21/2021] [Indexed: 12/05/2022] Open
Abstract
Vibrio cholerae cytolysin (VCC) is a β-barrel pore-forming toxin (β-PFT). Upon encountering the target cells, VCC forms heptameric β-barrel pores and permeabilizes the cell membranes. Structure-function mechanisms of VCC have been extensively studied in the past. However, the existence of any natural inhibitor for VCC has not been reported yet. In the present study, we show that curcumin can compromise the membrane-damaging activity of VCC. Curcumin is known to modulate a wide variety of biological processes and functions. However, the application of curcumin in the physiological scenario often gets limited due to its extremely poor solubility in the aqueous environment. Interestingly, we find that VCC can associate with the insoluble fraction of curcumin in the aqueous medium and thus gets separated from the solution phase. This, in turn, reduces the availability of VCC to attack the target membranes and thus blocks the membrane-damaging action of the toxin. We also observe that the soluble aqueous extract of curcumin, generated by the heat treatment, compromises the pore-forming activity of VCC. Interestingly, in the presence of such soluble extract of curcumin, VCC binds to the target membranes and forms the oligomeric assembly. However, such oligomers appear to be non-functional, devoid of the pore-forming activity. The ability of curcumin to bind to VCC and neutralize its membrane-damaging activity suggests that curcumin has the potential to act as an inhibitor of this potent bacterial β-PFT.
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Besançon H, Larpin Y, Babiychuk VS, Köffel R, Babiychuk EB. Engineered Liposomes Protect Immortalized Immune Cells from Cytolysins Secreted by Group A and Group G Streptococci. Cells 2022; 11:cells11010166. [PMID: 35011729 PMCID: PMC8749993 DOI: 10.3390/cells11010166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 12/30/2021] [Accepted: 01/02/2022] [Indexed: 12/10/2022] Open
Abstract
The increasing antibiotic resistance of bacterial pathogens fosters the development of alternative, non-antibiotic treatments. Antivirulence therapy, which is neither bacteriostatic nor bactericidal, acts by depriving bacterial pathogens of their virulence factors. To establish a successful infection, many bacterial pathogens secrete exotoxins/cytolysins that perforate the host cell plasma membrane. Recently developed liposomal nanotraps, mimicking the outer layer of the targeted cell membranes, serve as decoys for exotoxins, thus diverting them from attacking host cells. In this study, we develop a liposomal nanotrap formulation that is capable of protecting immortalized immune cells from the whole palette of cytolysins secreted by Streptococcus pyogenes and Streptococcus dysgalactiae subsp. equisimilis—important human pathogens that can cause life-threatening bacteremia. We show that the mixture of cholesterol-containing liposomes with liposomes composed exclusively of phospholipids is protective against the combined action of all streptococcal exotoxins. Our findings pave the way for further development of liposomal antivirulence therapy in order to provide more efficient treatment of bacterial infections, including those caused by antibiotic resistant pathogens.
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7
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Sengupta N, Mondal AK, Mishra S, Chattopadhyay K, Dutta S. Single-particle cryo-EM reveals conformational variability of the oligomeric VCC β-barrel pore in a lipid bilayer. J Cell Biol 2021; 220:212683. [PMID: 34617964 PMCID: PMC8504180 DOI: 10.1083/jcb.202102035] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 08/25/2021] [Accepted: 09/19/2021] [Indexed: 11/22/2022] Open
Abstract
Vibrio cholerae cytolysin (VCC) is a water-soluble, membrane-damaging, pore-forming toxin (PFT) secreted by pathogenic V. cholerae, which causes eukaryotic cell death by altering the plasma membrane permeability. VCC self-assembles on the cell surface and undergoes a dramatic conformational change from prepore to heptameric pore structure. Over the past few years, several high-resolution structures of detergent-solubilized PFTs have been characterized. However, high-resolution structural characterization of small β-PFTs in a lipid environment is still rare. Therefore, we used single-particle cryo-EM to characterize the structure of the VCC oligomer in large unilamellar vesicles, which is the first atomic-resolution cryo-EM structure of VCC. From our study, we were able to provide the first documented visualization of the rim domain amino acid residues of VCC interacting with lipid membrane. Furthermore, cryo-EM characterization of lipid bilayer–embedded VCC suggests interesting conformational variabilities, especially in the transmembrane channel, which could have a potential impact on the pore architecture and assist us in understanding the pore formation mechanism.
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Affiliation(s)
- Nayanika Sengupta
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Anish Kumar Mondal
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Punjab, India
| | - Suman Mishra
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Kausik Chattopadhyay
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Punjab, India
| | - Somnath Dutta
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
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8
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Mondal AK, Chattopadhyay K. Structures and functions of the membrane-damaging pore-forming proteins. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2021; 128:241-288. [PMID: 35034720 DOI: 10.1016/bs.apcsb.2021.07.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Pore-forming proteins (PFPs) of the diverse life forms have emerged as the potent cell-killing entities owing to their specialized membrane-damaging properties. PFPs have the unique ability to perforate the plasma membranes of their target cells, and they exert this functionality by creating oligomeric pores in the membrane lipid bilayer. Pathogenic bacteria employ PFPs as toxins to execute their virulence mechanisms, whereas in the higher vertebrates PFPs are deployed as the part of the immune system and to generate inflammatory responses. PFPs are the unique dimorphic proteins that are generally synthesized as water-soluble molecules, and transform into membrane-inserted oligomeric pore assemblies upon interacting with the target membranes. In spite of sharing very little sequence similarity, PFPs from diverse organisms display incredible structural similarity. Yet, at the same time, structure-function mechanisms of the PFPs document remarkable versatility. Such notions establish PFPs as the fascinating model system to explore variety of unsolved issues pertaining to the structure-function paradigm of the proteins that interact and act in the membrane environment. In this article, we discuss our current understanding regarding the structural basis of the pore-forming functions of the diverse class of PFPs. We attempt to highlight the similarities and differences in their structures, membrane pore-formation mechanisms, and their implications for the various biological processes, ranging from the bacterial virulence mechanisms to the inflammatory immune response generation in the higher animals.
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Affiliation(s)
- Anish Kumar Mondal
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, Punjab, India
| | - Kausik Chattopadhyay
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, Punjab, India.
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9
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Pinaud S, Tetreau G, Poteaux P, Galinier R, Chaparro C, Lassalle D, Portet A, Simphor E, Gourbal B, Duval D. New Insights Into Biomphalysin Gene Family Diversification in the Vector Snail Biomphalaria glabrata. Front Immunol 2021; 12:635131. [PMID: 33868258 PMCID: PMC8047071 DOI: 10.3389/fimmu.2021.635131] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Accepted: 03/08/2021] [Indexed: 11/30/2022] Open
Abstract
Aerolysins initially characterized as virulence factors in bacteria are increasingly found in massive genome and transcriptome sequencing data from metazoans. Horizontal gene transfer has been demonstrated as the main way of aerolysin-related toxins acquisition in metazoans. However, only few studies have focused on their potential biological functions in such organisms. Herein, we present an extensive characterization of a multigene family encoding aerolysins - named biomphalysin - in Biomphalaria glabrata snail, the intermediate host of the trematode Schistosoma mansoni. Our results highlight that duplication and domestication of an acquired bacterial toxin gene in the snail genome result in the acquisition of a novel and diversified toxin family. Twenty-three biomphalysin genes were identified. All are expressed and exhibited a tissue-specific expression pattern. An in silico structural analysis was performed to highlight the central role played by two distinct domains i) a large lobe involved in the lytic function of these snail toxins which constrained their evolution and ii) a small lobe which is structurally variable between biomphalysin toxins and that matched to various functional domains involved in moiety recognition of targets cells. A functional approach suggests that the repertoire of biomphalysins that bind to pathogens, depends on the type of pathogen encountered. These results underline a neo-and sub-functionalization of the biomphalysin toxins, which have the potential to increase the range of effectors in the snail’s immune arsenal.
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Affiliation(s)
- Silvain Pinaud
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Guillaume Tetreau
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Pierre Poteaux
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Richard Galinier
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Cristian Chaparro
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Damien Lassalle
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Anaïs Portet
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Elodie Simphor
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - Benjamin Gourbal
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
| | - David Duval
- IHPE, Univ Montpellier, CNRS, IFREMER, Univ Perpignan Via Domitia, Perpignan, France.,CNRS, IFREMER, University of Montpellier, Perpignan, France
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10
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Li Y, Li Y, Mengist HM, Shi C, Zhang C, Wang B, Li T, Huang Y, Xu Y, Jin T. Structural Basis of the Pore-Forming Toxin/Membrane Interaction. Toxins (Basel) 2021; 13:toxins13020128. [PMID: 33572271 PMCID: PMC7914777 DOI: 10.3390/toxins13020128] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 01/13/2021] [Accepted: 02/02/2021] [Indexed: 12/14/2022] Open
Abstract
With the rapid growth of antibiotic-resistant bacteria, it is urgent to develop alternative therapeutic strategies. Pore-forming toxins (PFTs) belong to the largest family of virulence factors of many pathogenic bacteria and constitute the most characterized classes of pore-forming proteins (PFPs). Recent studies revealed the structural basis of several PFTs, both as soluble monomers, and transmembrane oligomers. Upon interacting with host cells, the soluble monomer of bacterial PFTs assembles into transmembrane oligomeric complexes that insert into membranes and affect target cell-membrane permeability, leading to diverse cellular responses and outcomes. Herein we have reviewed the structural basis of pore formation and interaction of PFTs with the host cell membrane, which could add valuable contributions in comprehensive understanding of PFTs and searching for novel therapeutic strategies targeting PFTs and interaction with host receptors in the fight of bacterial antibiotic-resistance.
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Affiliation(s)
- Yajuan Li
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
| | - Yuelong Li
- Hefei National Laboratory for Physical Sciences at Microscale, Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, Division of Life Sciences and Medicine, School of Basic Medical Sciences, University of Science and Technology of China, Hefei 230027, China; (Y.L.); (H.M.M.); (C.Z.)
| | - Hylemariam Mihiretie Mengist
- Hefei National Laboratory for Physical Sciences at Microscale, Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, Division of Life Sciences and Medicine, School of Basic Medical Sciences, University of Science and Technology of China, Hefei 230027, China; (Y.L.); (H.M.M.); (C.Z.)
| | - Cuixiao Shi
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
| | - Caiying Zhang
- Hefei National Laboratory for Physical Sciences at Microscale, Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, Division of Life Sciences and Medicine, School of Basic Medical Sciences, University of Science and Technology of China, Hefei 230027, China; (Y.L.); (H.M.M.); (C.Z.)
| | - Bo Wang
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
| | - Tingting Li
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
| | - Ying Huang
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
| | - Yuanhong Xu
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
- Correspondence: (Y.X.); (T.J.); Tel.: +86-13505694447 (Y.X.); +86-17605607323 (T.J.)
| | - Tengchuan Jin
- Hefei National Laboratory for Physical Sciences at Microscale, Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, Division of Life Sciences and Medicine, School of Basic Medical Sciences, University of Science and Technology of China, Hefei 230027, China; (Y.L.); (H.M.M.); (C.Z.)
- Correspondence: (Y.X.); (T.J.); Tel.: +86-13505694447 (Y.X.); +86-17605607323 (T.J.)
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11
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Pore-forming toxins in infection and immunity. Biochem Soc Trans 2021; 49:455-465. [PMID: 33492383 DOI: 10.1042/bst20200836] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Revised: 01/02/2021] [Accepted: 01/06/2021] [Indexed: 12/14/2022]
Abstract
The integrity of the plasma membranes is extremely crucial for the survival and proper functioning of the cells. Organisms from all kingdoms of life employ specialized pore-forming proteins and toxins (PFPs and PFTs) that perforate cell membranes, and cause detrimental effects. PFPs/PFTs exert their damaging actions by forming oligomeric pores in the membrane lipid bilayer. PFPs/PFTs play important roles in diverse biological processes. Many pathogenic bacteria secrete PFTs for executing their virulence mechanisms. The immune system of the higher vertebrates employs PFPs to kill pathogen-infected cells and transformed cancer cells. The most obvious consequence of membrane pore-formation by the PFPs/PFTs is the killing of the target cells due to the disruption of the permeability barrier function of the plasma membranes. PFPs/PFTs can also activate diverse cellular processes that include activation of the stress-response pathways, induction of programmed cell death, and inflammation. Upon attack by the PFTs, host cells may also activate pathways to repair the injured membranes, restore cellular homeostasis, and trigger inflammatory immune responses. In this article, we present an overview of the diverse cellular responses that are triggered by the PFPs/PFTs, and their implications in the process of pathogen infection and immunity.
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12
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Mondal AK, Verma P, Sengupta N, Dutta S, Bhushan Pandit S, Chattopadhyay K. Tyrosine in the hinge region of the pore-forming motif regulates oligomeric β-barrel pore formation by Vibrio cholerae cytolysin. Mol Microbiol 2020; 115:508-525. [PMID: 33089544 DOI: 10.1111/mmi.14631] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 10/03/2020] [Indexed: 01/27/2023]
Abstract
β-barrel pore-forming toxins perforate cell membranes by forming oligomeric β-barrel pores. The most crucial step is the membrane-insertion of the pore-forming motifs that create the transmembrane β-barrel scaffold. Molecular mechanism that regulates structural reorganization of these pore-forming motifs during β-barrel pore-formation still remains elusive. Using Vibrio cholerae cytolysin as an archetypical example of the β-barrel pore-forming toxin, we show that a key tyrosine residue (Y321) in the hinge region of the pore-forming motif plays crucial role in this process. Mutation of Y321 abrogates oligomerization of the membrane-bound toxin protomers, and blocks subsequent steps of pore-formation. Our study suggests that the presence of Y321 in the hinge region of the pore-forming motif is crucial for the toxin molecule to sense membrane-binding, and to trigger essential structural rearrangements required for the subsequent oligomerization and pore-formation process. Such a regulatory mechanism of pore-formation by V. cholerae cytolysin has not been documented earlier in the structurally related β-barrel pore-forming toxins.
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Affiliation(s)
- Anish Kumar Mondal
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India
| | - Paras Verma
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India
| | - Nayanika Sengupta
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Somnath Dutta
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Shashi Bhushan Pandit
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India
| | - Kausik Chattopadhyay
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India
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Ramamurthy T, Nandy RK, Mukhopadhyay AK, Dutta S, Mutreja A, Okamoto K, Miyoshi SI, Nair GB, Ghosh A. Virulence Regulation and Innate Host Response in the Pathogenicity of Vibrio cholerae. Front Cell Infect Microbiol 2020; 10:572096. [PMID: 33102256 PMCID: PMC7554612 DOI: 10.3389/fcimb.2020.572096] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 08/19/2020] [Indexed: 02/06/2023] Open
Abstract
The human pathogen Vibrio cholerae is the causative agent of severe diarrheal disease known as cholera. Of the more than 200 "O" serogroups of this pathogen, O1 and O139 cause cholera outbreaks and epidemics. The rest of the serogroups, collectively known as non-O1/non-O139 cause sporadic moderate or mild diarrhea and also systemic infections. Pathogenic V. cholerae circulates between nutrient-rich human gut and nutrient-deprived aquatic environment. As an autochthonous bacterium in the environment and as a human pathogen, V. cholerae maintains its survival and proliferation in these two niches. Growth in the gastrointestinal tract involves expression of several genes that provide bacterial resistance against host factors. An intricate regulatory program involving extracellular signaling inputs is also controlling this function. On the other hand, the ability to store carbon as glycogen facilitates bacterial fitness in the aquatic environment. To initiate the infection, V. cholerae must colonize the small intestine after successfully passing through the acid barrier in the stomach and survive in the presence of bile and antimicrobial peptides in the intestinal lumen and mucus, respectively. In V. cholerae, virulence is a multilocus phenomenon with a large functionally associated network. More than 200 proteins have been identified that are functionally linked to the virulence-associated genes of the pathogen. Several of these genes have a role to play in virulence and/or in functions that have importance in the human host or the environment. A total of 524 genes are differentially expressed in classical and El Tor strains, the two biotypes of V. cholerae serogroup O1. Within the host, many immune and biological factors are able to induce genes that are responsible for survival, colonization, and virulence. The innate host immune response to V. cholerae infection includes activation of several immune protein complexes, receptor-mediated signaling pathways, and other bactericidal proteins. This article presents an overview of regulation of important virulence factors in V. cholerae and host response in the context of pathogenesis.
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Affiliation(s)
| | - Ranjan K Nandy
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Asish K Mukhopadhyay
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Shanta Dutta
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Ankur Mutreja
- Global Health-Infectious Diseases, Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Keinosuke Okamoto
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.,Collaborative Research Center of Okayama University for Infectious Diseases in India, National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Shin-Ichi Miyoshi
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - G Balakrish Nair
- Microbiome Laboratory, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
| | - Amit Ghosh
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India
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Mondal AK, Chattopadhyay K. Taking Toll on Membranes: Curious Cases of Bacterial β-Barrel Pore-Forming Toxins. Biochemistry 2019; 59:163-170. [DOI: 10.1021/acs.biochem.9b00783] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Anish Kumar Mondal
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, SAS Nagar, Manauli, Mohali, Punjab 140306, India
| | - Kausik Chattopadhyay
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, SAS Nagar, Manauli, Mohali, Punjab 140306, India
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16
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Revisiting the role of cholesterol in regulating the pore-formation mechanism of Vibrio cholerae cytolysin, a membrane-damaging β-barrel pore-forming toxin. Biochem J 2018; 475:3039-3055. [DOI: 10.1042/bcj20180387] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 09/03/2018] [Accepted: 09/10/2018] [Indexed: 11/17/2022]
Abstract
Vibrio cholerae cytolysin (VCC) is a β-barrel pore-forming toxin with potent membrane-damaging cell-killing activity. Previous studies employing the model membranes of lipid vesicles (liposomes) have shown that pore formation by VCC requires the presence of cholesterol in the liposome membranes. However, the exact role of cholesterol in the mode of action of VCC still remains unclear. Most importantly, implication of cholesterol, if any, in regulating the pore-formation mechanism of VCC in the biomembranes of eukaryotic cells remains unexplored. Here, we show that the presence of cholesterol promotes the interaction of VCC with the membrane lipid bilayer, when non-lipid-dependent interactions are absent. However, in the case of biomembranes of human erythrocytes, where accessory interactions are available, cholesterol appears to play a less critical role in the binding step. Nevertheless, in the absence of an optimal level of membrane cholesterol in the human erythrocytes, membrane-bound fraction of the toxin remains trapped in the form of abortive oligomeric assembly, devoid of functional pore-forming activity. Our study also shows that VCC exhibits a prominent propensity to associate with the cholesterol-rich membrane micro-domains of human erythrocytes. Interestingly, mutation of the cholesterol-binding ability of VCC does not block association with the cholesterol-rich membrane micro-domains on human erythrocytes. Based on these results, we propose that the specific cholesterol-binding ability of VCC does not appear to dictate its association with the cholesterol-rich micro-domains on human erythrocytes. Rather, targeting of VCC toward the membrane micro-domains of human erythrocytes possibly acts to facilitate the cholesterol-dependent pore-formation mechanism of the toxin.
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Xu L, Pan ZZ, Zhang J, Niu LY, Li J, Chen Z, Liu B, Zhu YJ, Chen QX. Exposure of helices α4 and α5 is required for insecticidal activity of Cry2Ab by promoting assembly of a prepore oligomeric structure. Cell Microbiol 2018; 20:e12827. [PMID: 29380507 DOI: 10.1111/cmi.12827] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 01/15/2018] [Accepted: 01/17/2018] [Indexed: 12/15/2022]
Abstract
Cry2Ab, a pore-forming toxin derived from Bacillus thuringiensis, is widely used as a bio-insecticide to control lepidopteran pests around the world. A previous study revealed that proteolytic activation of Cry2Ab by Plutella xylostella midgut juice was essential for its insecticidal activity against P. xylostella, although the exact molecular mechanism remained unknown. Here, we demonstrated for the first time that proteolysis of Cry2Ab uncovered an active region (the helices α4 and α5 in Domain I), which was required for the mode of action of Cry2Ab. Either the masking or the removal of helices α4 and α5 mediated the pesticidal activity of Cry2Ab. The exposure of helices α4 and α5 did not facilitate the binding of Cry2Ab to P. xylostella midgut receptors but did induce Cry2Ab monomer to aggregate and assemble a 250-kDa prepore oligomer. Site-directed mutagenesis assay was performed to generate Cry2Ab mutants site directed on the helices α4 and α5, and bioassays suggested that some Cry2Ab variants that could not form oligomers had significantly lowered their toxicities against P. xylostella. Taken together, our data highlight the importance of helices α4 and α5 in the mode of action of Cry2Ab and could lead to more detailed studies on the insecticidal activity of Cry2Ab.
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Affiliation(s)
- Lian Xu
- State Key Laboratory of Cellular Stress Biology, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian, People's Republic of China
| | - Zhi-Zhen Pan
- Agricultural Bio-Resources Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, Fujian, People's Republic of China
| | - Jing Zhang
- State Key Laboratory of Cellular Stress Biology, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian, People's Republic of China
| | - Li-Yang Niu
- State Key Laboratory of Cellular Stress Biology, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian, People's Republic of China
| | - Jie Li
- State Key Laboratory of Cellular Stress Biology, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian, People's Republic of China
| | - Zheng Chen
- Agricultural Bio-Resources Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, Fujian, People's Republic of China
| | - Bo Liu
- Agricultural Bio-Resources Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, Fujian, People's Republic of China
| | - Yu-Jing Zhu
- Agricultural Bio-Resources Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, Fujian, People's Republic of China
| | - Qing-Xi Chen
- State Key Laboratory of Cellular Stress Biology, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian, People's Republic of China
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Kathuria R, Chattopadhyay K. Vibrio choleraecytolysin: Multiple facets of the membrane interaction mechanism of aβ-barrel pore-forming toxin. IUBMB Life 2018; 70:260-266. [DOI: 10.1002/iub.1725] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Accepted: 02/05/2018] [Indexed: 12/22/2022]
Affiliation(s)
- Reema Kathuria
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences; Indian Institute of Science Education and Research Mohali; Manauli, Mohali Punjab India
| | - Kausik Chattopadhyay
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences; Indian Institute of Science Education and Research Mohali; Manauli, Mohali Punjab India
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Mondal AK, Sreekumar A, Kundu N, Kathuria R, Verma P, Gandhi S, Chattopadhyay K. Structural Basis and Functional Implications of the Membrane Pore-Formation Mechanisms of Bacterial Pore-Forming Toxins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1112:281-291. [DOI: 10.1007/978-981-13-3065-0_19] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Disulphide bond restrains the C-terminal region of thermostable direct hemolysin during folding to promote oligomerization. Biochem J 2016; 474:317-331. [PMID: 27784764 DOI: 10.1042/bcj20160728] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 10/14/2016] [Accepted: 10/25/2016] [Indexed: 11/17/2022]
Abstract
Pore-forming toxins (PFTs) are typically produced as water-soluble monomers, which upon interacting with target cells assemble into transmembrane oligomeric pores. Vibrio parahaemolyticus thermostable direct hemolysin (TDH) is an atypical PFT that exists as a tetramer in solution, prior to membrane binding. The TDH structure highlights a core β-sandwich domain similar to those found in the eukaryotic actinoporin family of PFTs. However, the TDH structure harbors an extended C-terminal region (CTR) that is not documented in the actinoporins. This CTR remains tethered to the β-sandwich domain through an intra-molecular disulphide bond. Part of the CTR is positioned at the inter-protomer interface in the TDH tetramer. Here we show that the truncation, as well as mutation, of the CTR compromise tetrameric assembly, and the membrane-damaging activity of TDH. Our study also reveals that intra-protomer disulphide bond formation during the folding/assembly process of TDH restrains the CTR to mediate its participation in the formation of inter-protomer contact, thus facilitating TDH oligomerization. However, once tetramerization is achieved, disruption of the disulphide bond does not affect oligomeric assembly. Our study provides critical insights regarding the regulation of the oligomerization mechanism of TDH, which has not been previously documented in the PFT family.
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Rai AK, Chattopadhyay K. Revisiting the oligomerization mechanism of Vibrio cholerae cytolysin, a beta-barrel pore-forming toxin. Biochem Biophys Res Commun 2016; 474:421-427. [DOI: 10.1016/j.bbrc.2016.05.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Accepted: 05/01/2016] [Indexed: 01/10/2023]
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De S, Bubnys A, Alonzo F, Hyun J, Lary JW, Cole JL, Torres VJ, Olson R. The Relationship between Glycan Binding and Direct Membrane Interactions in Vibrio cholerae Cytolysin, a Channel-forming Toxin. J Biol Chem 2015; 290:28402-28415. [PMID: 26416894 DOI: 10.1074/jbc.m115.675967] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Indexed: 12/19/2022] Open
Abstract
Bacterial pore-forming toxins (PFTs) are structurally diverse pathogen-secreted proteins that form cell-damaging channels in the membranes of host cells. Most PFTs are released as water-soluble monomers that first oligomerize on the membrane before inserting a transmembrane channel. To modulate specificity and increase potency, many PFTs recognize specific cell surface receptors that increase the local toxin concentration on cell membranes, thereby facilitating channel formation. Vibrio cholerae cytolysin (VCC) is a toxin secreted by the human pathogen responsible for pandemic cholera disease and acts as a defensive agent against the host immune system. Although it has been shown that VCC utilizes specific glycan receptors on the cell surface, additional direct contacts with the membrane must also play a role in toxin binding. To better understand the nature of these interactions, we conducted a systematic investigation of the membrane-binding surface of VCC to identify additional membrane interactions important in cell targeting. Through cell-based assays on several human-derived cell lines, we show that VCC is unlikely to utilize high affinity protein receptors as do structurally similar toxins from Staphylococcus aureus. Next, we identified a number of specific amino acid residues that greatly diminish the VCC potency against cells and investigated the interplay between glycan binding and these direct lipid contacts. Finally, we used model membranes to parse the importance of these key residues in lipid and cholesterol binding. Our study provides a complete functional map of the VCC membrane-binding surface and insights into the integration of sugar, lipid, and cholesterol binding interactions.
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Affiliation(s)
- Swastik De
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459
| | - Adele Bubnys
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459
| | - Francis Alonzo
- Department of Microbiology, New York University School of Medicine, New York, New York 10016
| | - Jinsol Hyun
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459
| | - Jeffrey W Lary
- Biotechnology-Bioservices Center, University of Connecticut, Storrs, Connecticut 06269
| | - James L Cole
- Biotechnology-Bioservices Center, University of Connecticut, Storrs, Connecticut 06269; Department of Molecular and Cell Biology and Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269
| | - Victor J Torres
- Department of Microbiology, New York University School of Medicine, New York, New York 10016
| | - Rich Olson
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459.
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Khilwani B, Chattopadhyay K. Signaling beyond Punching Holes: Modulation of Cellular Responses by Vibrio cholerae Cytolysin. Toxins (Basel) 2015; 7:3344-58. [PMID: 26308054 PMCID: PMC4549754 DOI: 10.3390/toxins7083344] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 08/12/2015] [Accepted: 08/14/2015] [Indexed: 01/20/2023] Open
Abstract
Pore-forming toxins (PFTs) are a distinct class of membrane-damaging cytolytic proteins that contribute significantly towards the virulence processes employed by various pathogenic bacteria. Vibrio cholerae cytolysin (VCC) is a prominent member of the beta-barrel PFT (beta-PFT) family. It is secreted by most of the pathogenic strains of the intestinal pathogen V. cholerae. Owing to its potent membrane-damaging cell-killing activity, VCC is believed to play critical roles in V. cholerae pathogenesis, particularly in those strains that lack the cholera toxin. Large numbers of studies have explored the mechanistic basis of the cell-killing activity of VCC. Consistent with the beta-PFT mode of action, VCC has been shown to act on the target cells by forming transmembrane oligomeric beta-barrel pores, thereby leading to permeabilization of the target cell membranes. Apart from the pore-formation-induced direct cell-killing action, VCC exhibits the potential to initiate a plethora of signal transduction pathways that may lead to apoptosis, or may act to enhance the cell survival/activation responses, depending on the type of target cells. In this review, we will present a concise view of our current understanding regarding the multiple aspects of these cellular responses, and their underlying signaling mechanisms, evoked by VCC.
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Affiliation(s)
- Barkha Khilwani
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences Indian Institute of Science Education and Research Mohali Sector 81, S. A. S. Nagar, Manauli PO 140306, Punjab, India.
| | - Kausik Chattopadhyay
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences Indian Institute of Science Education and Research Mohali Sector 81, S. A. S. Nagar, Manauli PO 140306, Punjab, India.
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