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Sea Anemones, Actinoporins, and Cholesterol. Int J Mol Sci 2022; 23:ijms23158771. [PMID: 35955905 PMCID: PMC9369217 DOI: 10.3390/ijms23158771] [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] [Received: 07/11/2022] [Revised: 08/01/2022] [Accepted: 08/05/2022] [Indexed: 11/17/2022] Open
Abstract
Spanish or Spanish-speaking scientists represent a remarkably populated group within the scientific community studying pore-forming proteins. Some of these scientists, ourselves included, focus on the study of actinoporins, a fascinating group of metamorphic pore-forming proteins produced within the venom of several sea anemones. These toxic proteins can spontaneously transit from a water-soluble fold to an integral membrane ensemble because they specifically recognize sphingomyelin in the membrane. Once they bind to the bilayer, they subsequently oligomerize into a pore that triggers cell-death by osmotic shock. In addition to sphingomyelin, some actinoporins are especially sensible to some other membrane components such as cholesterol. Our group from Universidad Complutense of Madrid has focused greatly on the role played by sterols in this water–membrane transition, a question which still remains only partially solved and constitutes the main core of the article below.
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Alvarez C, Soto C, Cabezas S, Alvarado-Mesén J, Laborde R, Pazos F, Ros U, Hernández AM, Lanio ME. Panorama of the Intracellular Molecular Concert Orchestrated by Actinoporins, Pore-Forming Toxins from Sea Anemones. Toxins (Basel) 2021; 13:toxins13080567. [PMID: 34437438 PMCID: PMC8402351 DOI: 10.3390/toxins13080567] [Citation(s) in RCA: 5] [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: 07/11/2021] [Revised: 08/05/2021] [Accepted: 08/06/2021] [Indexed: 12/25/2022] Open
Abstract
Actinoporins (APs) are soluble pore-forming proteins secreted by sea anemones that experience conformational changes originating in pores in the membranes that can lead to cell death. The processes involved in the binding and pore-formation of members of this protein family have been deeply examined in recent years; however, the intracellular responses to APs are only beginning to be understood. Unlike pore formers of bacterial origin, whose intracellular impact has been studied in more detail, currently, we only have knowledge of a few poorly integrated elements of the APs’ intracellular action. In this review, we present and discuss an updated landscape of the studies aimed at understanding the intracellular pathways triggered in response to APs attack with particular reference to sticholysin II, the most active isoform produced by the Caribbean Sea anemone Stichodactyla helianthus. To achieve this, we first describe the major alterations these cytolysins elicit on simpler cells, such as non-nucleated mammalian erythrocytes, and then onto more complex eukaryotic cells, including tumor cells. This understanding has provided the basis for the development of novel applications of sticholysins such as the construction of immunotoxins directed against undesirable cells, such as tumor cells, and the design of a cancer vaccine platform. These are among the most interesting potential uses for the members of this toxin family that have been carried out in our laboratory.
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Affiliation(s)
- Carlos Alvarez
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana (UH) and Laboratorio UH-Centro de Inmunología Molecular, Havana CP 11600, Cuba; (C.S.); (S.C.); (J.A.-M.); (R.L.); (F.P.); (U.R.); (M.E.L.)
- Correspondence:
| | - Carmen Soto
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana (UH) and Laboratorio UH-Centro de Inmunología Molecular, Havana CP 11600, Cuba; (C.S.); (S.C.); (J.A.-M.); (R.L.); (F.P.); (U.R.); (M.E.L.)
| | - Sheila Cabezas
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana (UH) and Laboratorio UH-Centro de Inmunología Molecular, Havana CP 11600, Cuba; (C.S.); (S.C.); (J.A.-M.); (R.L.); (F.P.); (U.R.); (M.E.L.)
| | - Javier Alvarado-Mesén
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana (UH) and Laboratorio UH-Centro de Inmunología Molecular, Havana CP 11600, Cuba; (C.S.); (S.C.); (J.A.-M.); (R.L.); (F.P.); (U.R.); (M.E.L.)
- Escuela de Ciencias Biológicas, Universidad Nacional, Heredia 40101, Costa Rica
| | - Rady Laborde
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana (UH) and Laboratorio UH-Centro de Inmunología Molecular, Havana CP 11600, Cuba; (C.S.); (S.C.); (J.A.-M.); (R.L.); (F.P.); (U.R.); (M.E.L.)
| | - Fabiola Pazos
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana (UH) and Laboratorio UH-Centro de Inmunología Molecular, Havana CP 11600, Cuba; (C.S.); (S.C.); (J.A.-M.); (R.L.); (F.P.); (U.R.); (M.E.L.)
| | - Uris Ros
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana (UH) and Laboratorio UH-Centro de Inmunología Molecular, Havana CP 11600, Cuba; (C.S.); (S.C.); (J.A.-M.); (R.L.); (F.P.); (U.R.); (M.E.L.)
- Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Joseph-Stelzmann-strasse 26, 50931 Cologne, Germany
| | - Ana María Hernández
- Immunobiology Division, Molecular Immunology Institute, Center of Molecular Immunology (CIM), Playa, Havana CP 11600, Cuba;
| | - María Eliana Lanio
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana (UH) and Laboratorio UH-Centro de Inmunología Molecular, Havana CP 11600, Cuba; (C.S.); (S.C.); (J.A.-M.); (R.L.); (F.P.); (U.R.); (M.E.L.)
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Palacios-Ortega J, García-Linares S, Rivera-de-Torre E, Heras-Márquez D, Gavilanes JG, Slotte JP, Martínez-Del-Pozo Á. Structural foundations of sticholysin functionality. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2021; 1869:140696. [PMID: 34246789 DOI: 10.1016/j.bbapap.2021.140696] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 07/05/2021] [Accepted: 07/06/2021] [Indexed: 01/22/2023]
Abstract
Actinoporins constitute a family of α pore-forming toxins produced by sea anemones. The soluble fold of these proteins consists of a β-sandwich flanked by two α-helices. Actinoporins exert their activity by specifically recognizing sphingomyelin at their target membranes. Once there, they penetrate the membrane with their N-terminal α-helices, a process that leads to the formation of cation-selective pores. These pores kill the target cells by provoking an osmotic shock on them. In this review, we examine the role and relevance of the structural features of actinoporins, down to the residue level. We look at the specific amino acids that play significant roles in the function of actinoporins and their fold. Particular emphasis is given to those residues that display a high degree of conservation across the actinoporin sequences known to date. In light of the latest findings in the field, the membrane requirements for pore formation, the effect of lipid composition, and the process of pore formation are also discussed.
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Affiliation(s)
- Juan Palacios-Ortega
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain; Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
| | - Sara García-Linares
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain
| | - Esperanza Rivera-de-Torre
- Department of Biochemistry and Biotechnology, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Diego Heras-Márquez
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain
| | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Álvaro Martínez-Del-Pozo
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain
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Functional and Structural Variation among Sticholysins, Pore-Forming Proteins from the Sea Anemone Stichodactyla helianthus. Int J Mol Sci 2020; 21:ijms21238915. [PMID: 33255441 PMCID: PMC7727798 DOI: 10.3390/ijms21238915] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 11/19/2020] [Accepted: 11/20/2020] [Indexed: 12/15/2022] Open
Abstract
Venoms constitute complex mixtures of many different molecules arising from evolution in processes driven by continuous prey-predator interactions. One of the most common compounds in these venomous cocktails are pore-forming proteins, a family of toxins whose activity relies on the disruption of the plasmatic membranes by forming pores. The venom of sea anemones, belonging to the oldest lineage of venomous animals, contains a large amount of a characteristic group of pore-forming proteins known as actinoporins. They bind specifically to sphingomyelin-containing membranes and suffer a conformational metamorphosis that drives them to make pores. This event usually leads cells to death by osmotic shock. Sticholysins are the actinoporins produced by Stichodactyla helianthus. Three different isotoxins are known: Sticholysins I, II, and III. They share very similar amino acid sequence and three-dimensional structure but display different behavior in terms of lytic activity and ability to interact with cholesterol, an important lipid component of vertebrate membranes. In addition, sticholysins can act in synergy when exerting their toxin action. The subtle, but important, molecular nuances that explain their different behavior are described and discussed throughout the text. Improving our knowledge about sticholysins behavior is important for eventually developing them into biotechnological tools.
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Evaluation of different approaches used to study membrane permeabilization by actinoporins on model lipid vesicles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183311. [DOI: 10.1016/j.bbamem.2020.183311] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 03/12/2020] [Accepted: 04/13/2020] [Indexed: 02/01/2023]
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Rivera-de-Torre E, Palacios-Ortega J, Garb JE, Slotte JP, Gavilanes JG, Martínez-Del-Pozo Á. Structural and functional characterization of sticholysin III: A newly discovered actinoporin within the venom of the sea anemone Stichodactyla helianthus. Arch Biochem Biophys 2020; 689:108435. [PMID: 32485153 DOI: 10.1016/j.abb.2020.108435] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 05/23/2020] [Accepted: 05/25/2020] [Indexed: 01/19/2023]
Abstract
Actinoporins are a family of pore-forming toxins produced by sea anemones as part of their venomous cocktail. These proteins remain soluble and stably folded in aqueous solution, but when interacting with sphingomyelin-containing lipid membranes, they become integral oligomeric membrane structures that form a pore permeable to cations, which leads to cell death by osmotic shock. Actinoporins appear as multigenic families within the genome of sea anemones: several genes encoding very similar actinoporins are detected within the same species. The Caribbean Sea anemone Stichodactyla helianthus produces three actinoporins (sticholysins I, II and III; StnI, StnII and StnIII) that differ in their toxic potency. For example, StnII is about four-fold more effective than StnI against sheep erythrocytes in causing hemolysis, and both show synergy. However, StnIII, recently discovered in the S. helianthus transcriptome, has not been characterized so far. Here we describe StnIII's spectroscopic and functional properties and show its potential to interact with the other Stns. StnIII seems to maintain the well-preserved fold of all actinoporins, characterized by a high content of β-sheet, but it is significantly less thermostable. Its functional characterization shows that the critical concentration needed to form active pores is higher than for either StnI or StnII, suggesting differences in behavior when oligomerizing on membrane surfaces. Our results show that StnIII is an interesting and unexpected piece in the puzzle of how this Caribbean Sea anemone species modulates its venomous activity.
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Affiliation(s)
- Esperanza Rivera-de-Torre
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Madrid, Spain; Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland; Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, USA
| | - Juan Palacios-Ortega
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Madrid, Spain; Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Jessica E Garb
- Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, USA
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Madrid, Spain
| | - Álvaro Martínez-Del-Pozo
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Madrid, Spain.
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Pore-forming toxins from sea anemones: from protein-membrane interaction to its implications for developing biomedical applications. ADVANCES IN BIOMEMBRANES AND LIPID SELF-ASSEMBLY 2020. [DOI: 10.1016/bs.abl.2020.02.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Pore-Forming Proteins from Cnidarians and Arachnids as Potential Biotechnological Tools. Toxins (Basel) 2019; 11:toxins11060370. [PMID: 31242582 PMCID: PMC6628452 DOI: 10.3390/toxins11060370] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 06/18/2019] [Accepted: 06/21/2019] [Indexed: 12/31/2022] Open
Abstract
Animal venoms are complex mixtures of highly specialized toxic molecules. Cnidarians and arachnids produce pore-forming proteins (PFPs) directed against the plasma membrane of their target cells. Among PFPs from cnidarians, actinoporins stand out for their small size and molecular simplicity. While native actinoporins require only sphingomyelin for membrane binding, engineered chimeras containing a recognition antibody-derived domain fused to an actinoporin isoform can nonetheless serve as highly specific immunotoxins. Examples of such constructs targeted against malignant cells have been already reported. However, PFPs from arachnid venoms are less well-studied from a structural and functional point of view. Spiders from the Latrodectus genus are professional insect hunters that, as part of their toxic arsenal, produce large PFPs known as latrotoxins. Interestingly, some latrotoxins have been identified as potent and highly-specific insecticides. Given the proteinaceous nature of these toxins, their promising future use as efficient bioinsecticides is discussed throughout this Perspective. Protein engineering and large-scale recombinant production are critical steps for the use of these PFPs as tools to control agriculturally important insect pests. In summary, both families of PFPs, from Cnidaria and Arachnida, appear to be molecules with promising biotechnological applications.
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Palacios-Ortega J, García-Linares S, Rivera-de-Torre E, Gavilanes JG, Martínez-Del-Pozo Á, Slotte JP. Sticholysin, Sphingomyelin, and Cholesterol: A Closer Look at a Tripartite Interaction. Biophys J 2019; 116:2253-2265. [PMID: 31146924 DOI: 10.1016/j.bpj.2019.05.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 05/05/2019] [Accepted: 05/10/2019] [Indexed: 02/06/2023] Open
Abstract
Actinoporins are a group of soluble toxic proteins that bind to membranes containing sphingomyelin (SM) and oligomerize to form pores. Sticholysin II (StnII) is a member of the actinoporin family produced by Stichodactyla helianthus. Cholesterol (Chol) is known to enhance the activity of StnII. However, the molecular mechanisms behind this activation have remained obscure, although the activation is not Chol specific but rather sterol specific. To further explore how bilayer lipids affect or are affected by StnII, we have used a multiprobe approach (fluorescent analogs of both Chol and SM) in combination with a series of StnII tryptophan (Trp) mutants to study StnII/bilayer interactions. First, we compared StnII bilayer permeabilization in the presence of Chol or oleoyl-ceramide (OCer). The comparison was done because both Chol and OCer have a 1-hydroxyl, which helps to orient the molecule in the bilayer (although OCer has additional polar functional groups). Both Chol and OCer also have increased affinity for SM, which StnII may recognize. However, our results show that only Chol was able to activate StnII-induced bilayer permeabilization; OCer failed to activate it. To further examine possible Chol/StnII interactions, we measured Förster resonance energy transfer between Trp in StnII and cholestatrienol, a fluorescent analog of Chol. We could show higher Förster resonance energy transfer efficiency between cholestatrienol and Trps in position 100 and 114 of StnII when compared to three other Trp positions further away from the bilayer binding region of StnII. Taken together, our results suggest that StnII was able to attract Chol to its vicinity, maybe by showing affinity for Chol. SM interactions are known to be important for StnII binding to bilayers, and Chol is known to facilitate subsequent permeabilization of the bilayers by StnII. Our results help to better understand the role of these important membrane lipids for the bilayer properties of StnII.
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Affiliation(s)
- Juan Palacios-Ortega
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain; Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Sara García-Linares
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain
| | | | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain
| | | | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
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Disassembling a cancer puzzle: Cell junctions and plasma membrane as targets for anticancer therapy. J Control Release 2018; 286:125-136. [PMID: 30030181 DOI: 10.1016/j.jconrel.2018.07.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Revised: 07/13/2018] [Accepted: 07/16/2018] [Indexed: 02/07/2023]
Abstract
Despite an enhanced permeability and retention effect typical of many solid tumors, drug penetration is not always sufficient. Possible strategies for the drug delivery improvement are a modification of the tumor cell-to-cell junctions and usage of cell membrane permeabilization proteins. In this review we discuss epithelial cell junctions as targets for a combined anticancer therapy and propose new possible sources of such agents. We suggest considering viral and bacterial pathogens disrupting epithelial layers as plentiful sources of new therapeutic agents for increasing tumor permeability for other effector agents. We also observe the application of pore forming proteins and peptides of different origin for cytoplasmic delivery of anti-cancer agents and consider the main obstacles of their use in vivo.
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Leychenko E, Isaeva M, Tkacheva E, Zelepuga E, Kvetkina A, Guzev K, Monastyrnaya M, Kozlovskaya E. Multigene Family of Pore-Forming Toxins from Sea Anemone Heteractis crispa. Mar Drugs 2018; 16:E183. [PMID: 29794988 PMCID: PMC6025637 DOI: 10.3390/md16060183] [Citation(s) in RCA: 16] [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: 04/24/2018] [Revised: 05/21/2018] [Accepted: 05/22/2018] [Indexed: 11/23/2022] Open
Abstract
Sea anemones produce pore-forming toxins, actinoporins, which are interesting as tools for cytoplasmic membranes study, as well as being potential therapeutic agents for cancer therapy. This investigation is devoted to structural and functional study of the Heteractis crispa actinoporins diversity. Here, we described a multigene family consisting of 47 representatives expressed in the sea anemone tentacles as prepropeptide-coding transcripts. The phylogenetic analysis revealed that actinoporin clustering is consistent with the division of sea anemones into superfamilies and families. The transcriptomes of both H. crispa and Heteractis magnifica appear to contain a large repertoire of similar genes representing a rapid expansion of the actinoporin family due to gene duplication and sequence divergence. The presence of the most abundant specific group of actinoporins in H. crispa is the major difference between these species. The functional analysis of six recombinant actinoporins revealed that H. crispa actinoporin grouping was consistent with the different hemolytic activity of their representatives. According to molecular modeling data, we assume that the direction of the N-terminal dipole moment tightly reflects the actinoporins' ability to possess hemolytic activity.
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Affiliation(s)
- Elena Leychenko
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
- School of Natural Sciences, Far Eastern Federal University, Sukhanova Street 8, Vladivostok 690091, Russia.
| | - Marina Isaeva
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
- School of Natural Sciences, Far Eastern Federal University, Sukhanova Street 8, Vladivostok 690091, Russia.
| | - Ekaterina Tkacheva
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Elena Zelepuga
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Aleksandra Kvetkina
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Konstantin Guzev
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Margarita Monastyrnaya
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Emma Kozlovskaya
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
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Self-homodimerization of an actinoporin by disulfide bridging reveals implications for their structure and pore formation. Sci Rep 2018; 8:6614. [PMID: 29700324 PMCID: PMC5920107 DOI: 10.1038/s41598-018-24688-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 04/04/2018] [Indexed: 11/17/2022] Open
Abstract
The Trp111 to Cys mutant of sticholysin I, an actinoporin from Stichodactyla helianthus sea anemone, forms a homodimer via a disulfide bridge. The purified dimer is 193 times less hemolytic than the monomer. Ultracentrifugation, dynamic light scattering and size-exclusion chromatography demonstrate that monomers and dimers are the only independent oligomeric states encountered. Indeed, circular dichroism and fluorescence spectroscopies showed that Trp/Tyr residues participate in homodimerization and that the dimer is less thermostable than the monomer. A homodimer three-dimensional model was constructed and indicates that Trp147/Tyr137 are at the homodimer interface. Spectroscopy results validated the 3D-model and assigned 85° to the disulfide bridge dihedral angle responsible for dimerization. The homodimer model suggests that alterations in the membrane/carbohydrate-binding sites in one of the monomers, as result of dimerization, could explain the decrease in the homodimer ability to form pores.
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