1
|
Dong J, Yan T, Yang Q, Song Y, Cheng B, Zhou S, Liu Y, Ai X. Palmatine Inhibits the Pathogenicity of Aeromonas hydrophila by Reducing Aerolysin Expression. Foods 2022. [PMCID: PMC9601346 DOI: 10.3390/foods11203250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Aeromonas hydrophila, an opportunistic aquatic pathogen widely spread in aquatic environments, is responsible for a number of infectious diseases in freshwater aquaculture. In addition, A. hydrophila can transmit from diseased fish to humans and results in health problems. The occurrence of antibiotic-resistant bacterial strains restricts the application of antibiotics and is responsible for failure of the treatment. Moreover, residues of antibiotics in aquatic products often threaten the quality and safety. Therefore, alternative strategies are called to deal with infections caused by antibiotic-resistant bacteria. Aerolysin, one of the most important virulence factors of A. hydrophila, is adopted as a unique anti-virulence target on the basis of the anti-virulence strategy to battling infections caused by A. hydrophila. Palmatine, an isoquinoline alkaloid from a variety of herbal medicines that showed no anti-A. hydrophila activity, could reduce hemolysis of the bacterium by decreasing aerolysin production. The results of the qPCR assay demonstrated that the transcription of the aerA gene was suppressed. Moreover, cell viability and in vivo study showed that palmatine treatment could decrease the pathogenicity of A. hydrophila both in vitro and in vivo. In summary, palmatine is a leading compound against A. hydrophila-associated infection in aquaculture by inhibiting the expression of aerolysin.
Collapse
Affiliation(s)
- Jing Dong
- Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Wuhan 430223, China
| | - Tianhui Yan
- College of Food Science and Engineering, Bohai University, Jinzhou 121013, China
| | - Qiuhong Yang
- Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Wuhan 430223, China
| | - Yi Song
- Chinese Academy of Fishery Sciences, Beijing 100039, China
| | - Bo Cheng
- Chinese Academy of Fishery Sciences, Beijing 100039, China
| | - Shun Zhou
- Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Wuhan 430223, China
| | - Yongtao Liu
- Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Wuhan 430223, China
| | - Xiaohui Ai
- Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Wuhan 430223, China
- Correspondence: ; Tel.: +86-027-81780298
| |
Collapse
|
2
|
Wang H, Ettedgui J, Forstater J, Robertson JWF, Reiner JE, Zhang H, Chen S, Kasianowicz JJ. Determining the Physical Properties of Molecules with Nanometer-Scale Pores. ACS Sens 2018; 3:251-263. [PMID: 29381331 DOI: 10.1021/acssensors.7b00680] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Nanometer-scale pores have been developed for the detection, characterization, and quantification of a wide range of analytes (e.g., ions, polymers, proteins, anthrax toxins, neurotransmitters, and synthetic nanoparticles) and for DNA sequencing. We describe the key requirements that made this method possible and how the technique evolved. Finally, we show that, despite sound theoretical work, which advanced both the conceptual framework and quantitative capability of the method, there are still unresolved questions that need to be addressed to further improve the technique.
Collapse
Affiliation(s)
- Haiyan Wang
- National Institute
of Standards and Technology Physical Measurement Laboratory, Gaithersburg, Maryland 20899, United States
- Shenzhen
Key Laboratory of Biomedical Engineering, School of Medicine, Shenzhen University, 3688 Nanhai Road, Shenzhen 508060, China
| | - Jessica Ettedgui
- National Institute
of Standards and Technology Physical Measurement Laboratory, Gaithersburg, Maryland 20899, United States
- Department
of Chemical Engineering, Columbia University New York, New York 10027, United States
| | - Jacob Forstater
- National Institute
of Standards and Technology Physical Measurement Laboratory, Gaithersburg, Maryland 20899, United States
- Department
of Chemical Engineering, Columbia University New York, New York 10027, United States
| | - Joseph W. F. Robertson
- National Institute
of Standards and Technology Physical Measurement Laboratory, Gaithersburg, Maryland 20899, United States
| | - Joseph E. Reiner
- Department
of Physics, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Huisheng Zhang
- Shenzhen
Key Laboratory of Biomedical Engineering, School of Medicine, Shenzhen University, 3688 Nanhai Road, Shenzhen 508060, China
| | - Siping Chen
- Shenzhen
Key Laboratory of Biomedical Engineering, School of Medicine, Shenzhen University, 3688 Nanhai Road, Shenzhen 508060, China
| | - John J. Kasianowicz
- National Institute
of Standards and Technology Physical Measurement Laboratory, Gaithersburg, Maryland 20899, United States
- Department
of Applied Physics Applied Mathematics, Columbia University New York, New York 10027, United States
| |
Collapse
|
3
|
Rees BJ, Tate M, Lynch AM, Thornton CA, Jenkins GJ, Walmsley RM, Johnson GE. Development of an in vitro PIG-A gene mutation assay in human cells. Mutagenesis 2017; 32:283-297. [PMID: 28057708 PMCID: PMC5907909 DOI: 10.1093/mutage/gew059] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 11/15/2016] [Indexed: 11/12/2022] Open
Abstract
Mutagens can be carcinogens, and traditionally, they have been identified in vitro using the Salmonella 'Ames' reverse mutation assay. However, prokaryotic DNA packaging, replication and repair systems are mechanistically very different to those in the humans we inevitably seek to protect. Therefore, for many years, mammalian cell line genotoxicity assays that can detect eukaryotic mutagens as well as clastogens and aneugens have been used. The apparent lack of specificity in these largely rodent systems, due partly to their mutant p53 status, has contributed to the use of animal studies to resolve data conflicts. Recently, silencing mutations at the PIG-A locus have been demonstrated to prevent glycophosphatidylinositol (GPI) anchor synthesis and consequentially result in loss of GPI-anchored proteins from the cell's extracellular surface. The successful exploitation of this mutant phenotype in animal studies has triggered interest in the development of an analogous in vitro PIG-A mutation screening assay. This article describes the development of a robust assay design using metabolically active human cells. The assay includes viability and cell membrane integrity assessment and conforms to the future ideas of the 21st-century toxicology testing.
Collapse
Affiliation(s)
- Benjamin J Rees
- Institute of Life Science, Swansea University Medical School, Singleton Park, Swansea, UK
| | - Matthew Tate
- Gentronix Ltd BioHub at Alderley Park, Alderley Edge, Cheshire, UK
| | | | - Catherine A Thornton
- Institute of Life Science, Swansea University Medical School, Singleton Park, Swansea, UK
| | - Gareth J Jenkins
- Institute of Life Science, Swansea University Medical School, Singleton Park, Swansea, UK
| | - Richard M Walmsley
- Gentronix Ltd BioHub at Alderley Park, Alderley Edge, Cheshire, UK
- Faculty of Life Sciences, University of Manchester, Manchester, UK
| | - George E Johnson
- Institute of Life Science, Swansea University Medical School, Singleton Park, Swansea, UK
| |
Collapse
|
4
|
Subramani PA, Narasimha RV, Balasubramanian R, Narala VR, Ganesh MR, Michael RD. Cytotoxic effects of Aeromonas hydrophila culture supernatant on peripheral blood leukocytes of Nile tilapia (Oreochromis niloticus): Possible presence of a secreted cytotoxic lectin. FISH & SHELLFISH IMMUNOLOGY 2016; 58:604-611. [PMID: 27702674 DOI: 10.1016/j.fsi.2016.09.061] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 09/26/2016] [Accepted: 09/30/2016] [Indexed: 06/06/2023]
Abstract
Number of exotoxins like haemolysin, leukocidin, aerolysin etc. were reported from Aeromonas hydrophila. In this study, we report the haemolytic and cytotoxic effect of A. hydrophila culture supernatant (CS) that is specifically inhibited by lactose and also by serum and mucus of Nile tilapia (Oreochromis niloticus). Hence, we assume the presence of a secreted lectin in the CS. CS is toxic to peripheral blood leukocytes (PBL) of O. niloticus as revealed by MTT assay and by flow cytometry. DNA laddering assay indicates that CS causes necrosis to PBL. As a result of necrosis, CS treated PBL showed increased production of reactive oxygen species as indicated by nitroblue tetrazolium and 2',7' -dichlorofluorescin diacetate assays. CS treated PBL showed reduced mRNA expression of TNF-α and IFN-γ genes. When CS was subjected to polyacrylamide gel electrophoresis, it showed a single band corresponding to the molecular weight of 45 kDa. However, upon concentrating the CS by ultrafiltration, many bands were visualized. Further studies at molecular level are required to unravel this macromolecular-leukocyte interaction which would ultimately benefit the aquaculture industry.
Collapse
Affiliation(s)
- Parasuraman Aiya Subramani
- Centre for Fish Immunology, Vels Institute of Science, Technology, and Advanced Studies (VISTAS), Pallavaram, Chennai, 600117, India
| | | | - Ramalakshmi Balasubramanian
- Centre for Fish Immunology, Vels Institute of Science, Technology, and Advanced Studies (VISTAS), Pallavaram, Chennai, 600117, India
| | | | - M R Ganesh
- Interdisciplinary Institute of Indian System of Medicine, SRM University, Kattankulathur, 603203, India
| | - R Dinakaran Michael
- Centre for Fish Immunology, Vels Institute of Science, Technology, and Advanced Studies (VISTAS), Pallavaram, Chennai, 600117, India.
| |
Collapse
|
5
|
Hesperidin inhibits inflammatory response induced by Aeromonas hydrophila infection and alters CD4+/CD8+ T cell ratio. Mediators Inflamm 2014; 2014:393217. [PMID: 24891765 PMCID: PMC4033591 DOI: 10.1155/2014/393217] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Accepted: 03/21/2014] [Indexed: 12/26/2022] Open
Abstract
Background. Aeromonas hydrophila is an opportunistic bacterial pathogen that is associated with a number of human diseases. Hesperidin (HES) has been reported to exert antioxidant and anti-inflammatory activities. Objectives. The aim of this study was to investigate the potential effect of HES treatment on inflammatory response induced by A. hydrophila infection in murine. Methods. A. hydrophila-infected mice were treated with HES at 250 mg/kg b.wt./week for 4 consecutive weeks. Phagocytosis, reactive oxygen species production, CD4+/CD8+ T cell ratio, and CD14 expression on intestinal infiltrating monocytes were evaluated. The expression of E-selectin and intercellular adhesion molecule 1 on stimulated HUVECs and RAW macrophage was evaluated. Results. Percentage of CD4+ T cells in the intestinal tissues of infected treated mice was highly significantly increased; however, phagocytic index, ROS production, CD8+ T cells percentage, and CD14 expression on monocytes were significantly reduced. On the other hand, HES significantly inhibited A-LPS- and A-ECP-induced E-selectin and ICAM-1 expression on HUVECs and ICAM-1 expression on RAW macrophage. Conclusion. Present data indicated that HES has a potential role in the suppression of inflammatory response induced by A. hydrophila toxins through downmodulation of ROS production and CD14 and adhesion molecules expression, as well as increase of CD4+/CD8+ cell ratio.
Collapse
|
6
|
Shimada H, Kitada S. Mega assemblages of oligomeric aerolysin-like toxins stabilized by toxin-associating membrane proteins. J Biochem 2010; 149:103-15. [PMID: 20971989 DOI: 10.1093/jb/mvq124] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Most β pore-forming toxins need to be oligomerized via receptors in order to form membrane pores. Though oligomerizing toxins frequently form SDS-resistant oligomers, it was questionable whether SDS-resistant oligomers reflected native functional toxin complexes. In order to elucidate the essence of the cytocidal assemblages, oligomers of aerolysin-like toxins, aerolysin, parasporin-2 and epsilon toxin, were examined with or without SDS. On Blue Native PAGE, each toxin, which had been solubilized from target cells with mild detergent, was a much larger complex (nearly 1 MDa) than the typical SDS-resistant oligomers (∼200 kDa). Size exclusion chromatography confirmed the huge toxin complexes. While a portion of the huge complexes were sensitive to proteases, SDS-resistant oligomers resist the proteolysis. Presumably the core toxin complexes remained intact while the cellular proteins were degraded. Moreover, intermediate complexes, which included no SDS-resistant oligomers, could be detected at lower temperatures. This study provides evidence for huge functional complexes of β pore-forming toxins and emphasizes their potential variance in composition.
Collapse
Affiliation(s)
- Hiroyasu Shimada
- Department of Bioscience and Bioinfomatics, Kyushu Institute of Technology, Iizuka, Fukuoka 820-8502, Japan
| | | |
Collapse
|
7
|
Kloft N, Busch T, Neukirch C, Weis S, Boukhallouk F, Bobkiewicz W, Cibis I, Bhakdi S, Husmann M. Pore-forming toxins activate MAPK p38 by causing loss of cellular potassium. Biochem Biophys Res Commun 2009; 385:503-6. [PMID: 19497299 DOI: 10.1016/j.bbrc.2009.05.121] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Accepted: 05/14/2009] [Indexed: 01/15/2023]
Abstract
Mitogen activated protein kinase (MAPK) p38 has emerged as a survival protein in cells that are attacked by bacterial toxins forming small membrane pores. Activation of p38 by pore forming toxins (PFT) has been attributed to osmotic stress, but here we show that loss of K+ is likely to be the critical parameter. Several lines of evidence support this conclusion: first, osmoprotection did not prevent p38-phosphorylation in alpha-toxin-loaded cells. Second, treatment of cells with a K+ ionophore, or simple incubation in K+-free medium sufficed to cause robust p38-phosphorylation. Third, media containing high [K+] prevented p38-activation by Staphylococcus aureus alpha-toxin, Vibrio cholerae cytolysin (VCC), Streptolysin O (SLO), or Escherichia coli hemolysin (HlyA), but did not impair activation by H2O2. Fourth, potential roles of LPS, TLR4, or calcium-influx were ruled out. Therefore, we propose that PFT trigger the p38 MAPK-pathway by causing loss of cellular K+.
Collapse
Affiliation(s)
- Nicole Kloft
- Institut für Medizinische Mikrobiologie und Hygiene, Universitätsmedizin, Johannes Gutenberg-Universität, Mainz, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Parker MW, Feil SC. Pore-forming protein toxins: from structure to function. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2005; 88:91-142. [PMID: 15561302 DOI: 10.1016/j.pbiomolbio.2004.01.009] [Citation(s) in RCA: 339] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Pore-forming protein toxins (PFTs) are one of Nature's most potent biological weapons. An essential feature of their toxicity is the remarkable property that PFTs can exist either in a stable water-soluble state or as an integral membrane pore. In order to convert from the water-soluble to the membrane state, the toxin must undergo large conformational changes. There are now more than a dozen PFTs for which crystal structures have been determined and the nature of the conformational changes they must undergo is beginning to be understood. Although they differ markedly in their primary, secondary, tertiary and quaternary structures, nearly all can be classified into one of two families based on the types of pores they are thought to form: alpha-PFTs or beta-PFTs. Recent work suggests a number of common features in the mechanism of membrane insertion may exist for each class.
Collapse
Affiliation(s)
- Michael W Parker
- Biota Structural Biology Laboratory, St. Vincent's Institute of Medical Research, 9 Princes Street, Fitzroy, Victoria 3065, Australia.
| | | |
Collapse
|
9
|
Kirov SM, Barnett TC, Pepe CM, Strom MS, Albert MJ. Investigation of the role of type IV Aeromonas pilus (Tap) in the pathogenesis of Aeromonas gastrointestinal infection. Infect Immun 2000; 68:4040-8. [PMID: 10858220 PMCID: PMC101691 DOI: 10.1128/iai.68.7.4040-4048.2000] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although there is substantial evidence that type IV pili purified from diarrhea-associated Aeromonas species (designated Bfp for bundle-forming pilus) are intestinal colonization factors (S. M. Kirov, L. A. O'Donovan, and K. Sanderson, Infect. Immun. 67:5447-5454, 1999), nothing is known regarding the function of a second family of Aeromonas type IV pili (designated Tap for type IV Aeromonas pilus), identified following the cloning of a pilus biogenesis gene cluster tapABCD. Related pilus gene clusters are widely conserved among gram-negative bacteria, but their significance for virulence has been controversial. To investigate the role of Tap pili in Aeromonas pathogenesis, mutants of Aeromonas strains (a fish isolate of A. hydrophila and a human dysenteric isolate of A. veronii bv. sobria) were prepared by insertional inactivation of the tapA gene which encodes the type IV pilus subunit protein, TapA. Exotoxic activities were unaffected by the mutation in tapA. Inactivation of tapA had no effect on the bacterial adherence of these two isolates to HEp-2 cells. For the A. veronii bv. sobria isolate, adhesion to Henle 407 intestinal cells and to human intestinal tissue was also unaffected. There was no significant effect on the duration of colonization or incidence of diarrhea when the A. veronii bv. sobria strain was tested in the removable intestinal tie adult rabbit diarrhea model or on its ability to colonize infant mice. Evidence was obtained that demonstrated that TapA was expressed by both Aeromonas species and was present on the cell surface, although if assembled into pili this pilus type appears to be an uncommon one under standard bacterial growth conditions. Further studies into factors which may influence Tap expression are required, but the present study suggests that Tap pili may not be as significant as Bfp pili for Aeromonas intestinal colonization.
Collapse
Affiliation(s)
- S M Kirov
- Discipline of Pathology, University of Tasmania, Hobart 7001, Tasmania, Australia.
| | | | | | | | | |
Collapse
|
10
|
Lange S, Kauschke E, Mohrig W, Cooper EL. Biochemical characteristics of Eiseniapore, a pore-forming protein in the coelomic fluid of earthworms. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 262:547-56. [PMID: 10336641 DOI: 10.1046/j.1432-1327.1999.00407.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cytolytic protein Eiseniapore (38 kDa) from coelomic fluid of the earthworm Eisenia fetida functionally requires sphingomyelin as revealed by using mammalian erythrocytes and phospholipid vesicles. The effects of ions, glycoproteins and phospholipids were investigated for the two-step Eiseniapore action mode, binding and pore formation in different assays. Eiseniapore lysis is activated by thiol groups but inhibited by metal ions. Eiseniapore binding to target membranes is inhibited by Eiseniapore-regulating factor, vitronectin, heparin and lysophosphatidylcholine. Ca2+ and Mg2+ were found to be not necessary for membrane binding or lytic activity. Sphingomyelin was essential for Eiseniapore-induced leakage of liposomes. We describe a cytolytic protein/toxin in Eiseniapore which differs from the established classification; it can be activated by thiol groups and is inhibited by sphingomyelin. Electron microscopy of erythrocyte membranes confirmed ring-shaped structures (pores) with a central channel with outer (10 nm) and inner (3 nm) diameters as shown previously [Lange, S., Nüssler, F., Kauschke, E., Lutsch, G., Cooper, E.L. & Herrmann, A. (1997) J. Biol. Chem. 272, 20 884-20 892] using artificial membranes. Functional evidence of pore formation by Eiseniapore was revealed as protection of lysis by carbohydrates occurred at an effective diameter above 3 nm. From these results, we suggest a plausible explanation for the mechanism by which components of the earthworm's immune system destroy non-self components.
Collapse
Affiliation(s)
- S Lange
- Mathematisch-Naturwissenschaftliche Fakultät I Institut für Biologie/Biophysik, Humboldt Universität Berlin, Germany
| | | | | | | |
Collapse
|
11
|
6.10 Bacterial Exotoxins. J Microbiol Methods 1998. [DOI: 10.1016/s0580-9517(08)70291-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
|
12
|
Barnett TC, Kirov SM, Strom MS, Sanderson K. Aeromonas spp. possess at least two distinct type IV pilus families. Microb Pathog 1997; 23:241-7. [PMID: 9344785 DOI: 10.1006/mpat.1997.0152] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Type IV pili have been purified from strains of most of the Aeromonas species associated with gastroenteritis (A. veronii biovar sobria, A. hydrophila, A. trota and A. caviae). They appear to be a related family (molecular mass of pilin 19 to 23 kDa) with a tendency to bundle-formation. Hence, we have designated them 'bundle-forming pili' (Bfp). A type IV pilus biogenesis gene cluster (tapABCD) recently cloned from a strain of A. hydrophila, however, encoded a 17 kDa pilin which differed significantly in its N-terminal amino acid sequence from the Bfp pilins. This paper describes the cloning of part (tapA and approximately 20% of tapB) of a homologous pilin gene cluster from a Bfp-positive strain of A. veronii biovar sobria, and presents evidence that the entire pilin gene cluster (tapABCD) is present in this strain. The predicted N-terminal amino acid sequence of the pilin encoded by the A. veronii biovar sobria tapA differed markedly from the corresponding sequence of its Bfp pilin, and those of the Bfp purified from other Aeromonas strains and species. Probing with tapA and tapD genes showed that these Bfp-positive Aeromonas strains also possessed the Tap gene cluster. TapA proteins of A. veronii biovar sobria and A. hydrophila shared 53% identity and 63% homology. We conclude that Aeromonas species are potentially able to express at least two distinct families of type IV pili (Bfp and Tap).
Collapse
Affiliation(s)
- T C Barnett
- Division of Pathology, University of Tasmania, GPO 252-29, Hobart, Tasmania, 7001, Australia
| | | | | | | |
Collapse
|
13
|
Abstract
Channel-forming bacterial toxins undergo a series of remarkable changes in solubility, oligomerization state, structure and dynamics during the processes of membrane binding, assembly, membrane insertion and channel formation. Recent high-resolution crystal structures of channel-forming toxins, in both water-soluble and membrane-bound, channel-formed states, have brought a wealth of new information to bear on issues of structure, mechanism and function.
Collapse
Affiliation(s)
- E Gouaux
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.
| |
Collapse
|
14
|
Vécsey-Semjén B, Möllby R, van der Goot FG. Partial C-terminal unfolding is required for channel formation by staphylococcal alpha-toxin. J Biol Chem 1996; 271:8655-60. [PMID: 8621496 DOI: 10.1074/jbc.271.15.8655] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The pore-forming alpha-toxin from Staphylococcus aureus is secreted as a soluble monomeric protein. In order to form a transmembrane channel, the protein has to undergo oligomerization and membrane insertion. Previous studies have shown that channel formation is favored by acidic pH. We have analyzed the effect of pH on the kinetics of channel formation as well as on the conformation of the toxin. Using a variety of spectroscopic probes for protein structure, we have shown that alpha-toxin unfolded upon acidification and that the unfolding process occurred in at least three steps. The various steps could be selectively affected by modifying the salt concentration or the temperature. This unfolding was, however, only partial as the secondary structure remained native-like as witnessed by far UV CD measurements. The first unfolding step, corresponding to a region of the C-terminal half of the toxin, is of particular importance as it coincided with the exposure of hydrophobic patches on the surface of the protein as well as with the onset of channel formation. Our observations strongly suggest that transition of the C-terminal half of alpha-toxin to a molten globule-like state is required for channel formation.
Collapse
Affiliation(s)
- B Vécsey-Semjén
- Département de Biochimie, Université de Genève, 30 quai E. Ansermet, 1211 Genève, Switzerland
| | | | | |
Collapse
|
15
|
Tschödrich-Rotter M, Kubitscheck U, Ugochukwu G, Buckley JT, Peters R. Optical single-channel analysis of the aerolysin pore in erythrocyte membranes. Biophys J 1996; 70:723-32. [PMID: 8789089 PMCID: PMC1224972 DOI: 10.1016/s0006-3495(96)79612-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Scanning microphotolysis (Scamp), a recently developed photobleaching technique, was used to analyze the transport of two small organic anions and one inorganic cation through single pores formed in human erythrocyte membranes by the channel-forming toxin aerolysin secreted by Aeromonas species. The transport rate constants of erythrocyte ghosts carrying a single aerolysin pore were determined to be (1.83 +/- 0.43) x 10(-3) s-1 for Lucifer yellow, (0.33 +/- 0.10) x 10(-3) s-1 for carboxyfluorescein, and (8.20 +/- 2.30) x 10(-3) s-1 for Ca2+. The radius of the aerolysin pore was derived from the rate constants to be 19-23 A, taking steric hindrance and viscous drag into account. The size of the Ca2+ rate constant implies that at physiological extracellular Ca2+ concentrations (> 1 mM) the intracellular Ca2+ concentration would be elevated to the critical level of > 1 microM in much less than a second after formation of a single aerolysin pore in the plasma membrane. Thus changes in the levels of Ca2+ or other critical intracellular components may be more likely to cause cell death than osmotic imbalance.
Collapse
Affiliation(s)
- M Tschödrich-Rotter
- Institut für Medizinische Physik und Biophysik, Westfälische Wilhelms-Universität, Münster, Germany
| | | | | | | | | |
Collapse
|
16
|
|
17
|
Abstract
Protein crystallography is the study of the three-dimensional shapes of proteins at near atomic resolution. The field has provided a tremendous insight into the workings of numerous biological processes over the last few decades. The field is presently undergoing a massive worldwide expansion, not only in academic laboratories but also in the pharmaceutical industry. The main driving force for this expansion is the possibility of using the three-dimensional atomic structures of proteins to design lead drugs and to improve the action of existing drugs. This expansion in the field has been mirrored in Australia where the number of protein crystallography groups has more than trebled in the last five years. The work in the Protein Crystallography Unit at St Vincent's Institute of Medical Research has centered on the structural elucidation of membrane proteins and structure-based inhibitor studies of a protein family that attack certain anti-cancer drugs.
Collapse
Affiliation(s)
- M W Parker
- Ian Potter Foundation Protein Crystallography Laboratory, St. Vincent's Institute of Medical Research, Melbourne, Vic
| |
Collapse
|