51
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Nguyen VT, Higuchi H, Kamio Y. Controlling pore assembly of staphylococcal gamma-haemolysin by low temperature and by disulphide bond formation in double-cysteine LukF mutants. Mol Microbiol 2002; 45:1485-98. [PMID: 12354220 DOI: 10.1046/j.1365-2958.2002.03125.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Staphylococcal LukF and Hlg2 are water-soluble monomers of gamma-haemolysin that assemble into oligomeric pores on the erythrocyte membranes. Here, we have created double-cysteine LukF mutants, in which single disulphide bonds connect either the prestem domain and the cap domain (V12C-T136C, Cap-Stem), or two beta-strands within the prestem domain (T117C-T136C, Stem-Stem) to control pore assembly of gamma-haemolysin at intermediate stages. The disulphide-trapped mutants were inactive in erythrocyte lysis, but gained full haemolytic activity if the disulphide bonds were reduced. The disulphide bonds blocked neither the membrane binding ability nor the intermediate prepore oligomerization, but efficiently inhibited the transition from prepores to pores. The prepores of Cap-Stem were dissociated into monomers in 1% SDS. In contrast, the prepores of Stem-Stem were stable in SDS and had ring-shaped structures similar to those of wild-type LukF, as observed by transmission electron microscopy. The transition of both mutants from prepores to pores could even be achieved by reducing disulphide bonds at low temperature (2 degrees C), whereas prepore oligomerization was effectively inhibited by low temperature. Finally, real-time transition of Stem-Stem from prepores to pores on ghost cells, visualized using a Ca2+-sensitive fluorescent indicator (Rhod2), was shown by the sequential appearance of fluorescence spots, indicating pore-opening events. Taken together, these data indicate that the prepores are legitimate intermediates during gamma-haemolysin pore assembly, and that conformational changes around residues 117 and 136 of the prestem domain are essential for pore formation, but not for membrane binding or prepore oligomerization. We propose a mechanism for gamma-haemolysin pore assembly based on the demonstrated intermediates.
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Affiliation(s)
- Vananh T Nguyen
- Department of Molecular and Cell Biology, School of Agricultural Science, Tohoku University, Sendai, Japan
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52
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Werner S, Colin DA, Coraiola M, Menestrina G, Monteil H, Prévost G. Retrieving biological activity from LukF-PV mutants combined with different S components implies compatibility between the stem domains of these staphylococcal bicomponent leucotoxins. Infect Immun 2002; 70:1310-8. [PMID: 11854215 PMCID: PMC127755 DOI: 10.1128/iai.70.3.1310-1318.2002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bicomponent leucotoxins, such as Panton-Valentine leucocidin, are composed of two classes of proteins, a class S protein such as LukS-PV, which bears the cell membrane binding function, and a class F protein such as LukF-PV, which interacts to form a bipartite hexameric pore. These leucotoxins induce cell activation, linked to a Ca(2+) influx, and pore formation as two consecutive and independently inhibitable events. Knowledge of the LukF-PV monomer structure has indicated that the stem domain is folded into three antiparallel beta-strands in the water-soluble form and has to refold into a transmembrane beta-hairpin during pore formation. To investigate the requirements for the cooperative assembly of the stems of the S and F components to produce biological activity, we introduced multiple deletions or single point mutations into the stem domains of LukF-PV and HlgB. While the binding of the mutated proteins was weakly dependent on these changes, Ca(2+) influx and pore formation were affected differently, confirming that they are independent events. Ca(2+) entry into human polymorphonuclear cells requires oligomerization and may follow the formation of a prepore. The activity of some of the LukF-PV mutants, carrying the shorter deletions, was actually improved. This demonstrated that a crucial event in the action of these toxins is the transition of the prefolded stem into the extended beta-hairpins and that this step may be facilitated by small deletions that remove some of the interactions stabilizing the folded structure.
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Affiliation(s)
- S Werner
- Laboratoire de Physiopathologie et d'Antibiologie des Infections Bactériennes Emergentes et Nosocomiales, Institut de Bactériologie de la Faculté de Médecine, Université Louis Pasteur, F-67000 Strasbourg, France
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53
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Rose F, Dahlem G, Guthmann B, Grimminger F, Maus U, Hänze J, Duemmer N, Grandel U, Seeger W, Ghofrani HA. Mediator generation and signaling events in alveolar epithelial cells attacked by S. aureus alpha-toxin. Am J Physiol Lung Cell Mol Physiol 2002; 282:L207-14. [PMID: 11792625 DOI: 10.1152/ajplung.00156.2001] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Staphylococcus aureus alpha-toxin is a pore-forming bacterial exotoxin that has been implicated as a significant virulence factor in human staphylococcal diseases. In primary cultures of rat pneumocyte type II cells and the human A549 alveolar epithelial cell line, purified alpha-toxin provoked rapid-onset phosphatidylinositol (PtdIns) hydrolysis as well as liberation of nitric oxide and the prostanoids PGE(2), PGI(2), and thromboxane A(2). In addition, sustained upregulation of proinflammatory interleukin (IL)-8 mRNA expression and protein secretion occurred. "Priming" with low-dose IL-1beta markedly enhanced the IL-8 response to alpha-toxin, which was then accompanied by IL-6 appearance. The cytokine response was blocked by the intracellular Ca(2+)-chelating reagent 1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid, the protein kinase C inhibitor bis-indolyl maleimide I, as well as two independent inhibitors of nuclear factor-kappaB activation, pyrrolidine dithiocarbamate and caffeic acid phenethyl ester. We conclude that alveolar epithelial cells are highly reactive target cells of staphylococcal alpha-toxin. alpha-Toxin pore-associated transmembrane Ca(2+) flux and PtdIns hydrolysis-related signaling with downstream activation of protein kinase C and nuclear translocation of nuclear factor-kappaB are suggested to represent important underlying mechanisms. Such reactivity of the alveolar epithelial cells may be relevant for pathogenic sequelae in staphylococcal lung disease.
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Affiliation(s)
- Frank Rose
- Department of Internal Medicine, Justus-Liebig University, Giessen D-35392, Germany.
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54
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Bantel H, Sinha B, Domschke W, Peters G, Schulze-Osthoff K, Jänicke RU. alpha-Toxin is a mediator of Staphylococcus aureus-induced cell death and activates caspases via the intrinsic death pathway independently of death receptor signaling. J Cell Biol 2001; 155:637-48. [PMID: 11696559 PMCID: PMC2198876 DOI: 10.1083/jcb.200105081] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Infections with Staphylococcus aureus, a common inducer of septic and toxic shock, often result in tissue damage and death of various cell types. Although S. aureus was suggested to induce apoptosis, the underlying signal transduction pathways remained elusive. We show that caspase activation and DNA fragmentation were induced not only when Jurkat T cells were infected with intact bacteria, but also after treatment with supernatants of various S. aureus strains. We also demonstrate that S. aureus-induced cell death and caspase activation were mediated by alpha-toxin, a major cytotoxin of S. aureus, since both events were abrogated by two different anti-alpha-toxin antibodies and could not be induced with supernatants of an alpha-toxin-deficient S. aureus strain. Furthermore, alpha-toxin-induced caspase activation in CD95-resistant Jurkat sublines lacking CD95, Fas-activated death domain, or caspase-8 but not in cells stably expressing the antiapoptotic protein Bcl-2. Together with our finding that alpha-toxin induces cytochrome c release in intact cells and, interestingly, also from isolated mitochondria in a Bcl-2-controlled manner, our results demonstrate that S. aureus alpha-toxin triggers caspase activation via the intrinsic death pathway independently of death receptors. Hence, our findings clearly define a signaling pathway used in S. aureus-induced cytotoxicity and may provide a molecular rationale for future therapeutic interventions in bacterial infections.
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Affiliation(s)
- H Bantel
- Department of Immunology and Cell Biology, University of Münster, 48149 Münster, Germany
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55
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Menestrina G, Serra MD, Prévost G. Mode of action of beta-barrel pore-forming toxins of the staphylococcal alpha-hemolysin family. Toxicon 2001; 39:1661-72. [PMID: 11595629 DOI: 10.1016/s0041-0101(01)00153-2] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Staphylococcal alpha-hemolysin is the prototype of a family of bacterial exotoxins with membrane-damaging function, which share sequence and structure homology. These toxins are secreted in a soluble form which finally converts into a transmembrane pore by assembling an oligomeric beta-barrel, with hydrophobic residues facing the lipids and hydrophilic residues facing the lumen of the channel. Besides alpha-hemolysin the family includes other single chain toxins forming homo-oligomers, e.g. beta-toxin of Clostridium perfringens, hemolysin II and cytotoxin K of Bacillus cereus, but also the staphylococcal bi-component toxins, like gamma-hemolysins and leucocidins, which are only active as the combination of two similar proteins which form hetero-oligomers. The molecular basis of membrane insertion has become clearer after the determination of the crystal structure of both the oligomeric pore and the soluble monomer. Studies on this family of beta-barrel pore-forming toxins are important for many aspects: (i) they are involved in serious pathologies of humans and farmed animals, (ii) they are a good model system to investigate protein-membrane interaction and (iii) they are the basic elements for the construction of nanopores with biotechnological applications in various fields.
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Affiliation(s)
- G Menestrina
- CNR-ITC Centro Fisica Stati Aggregati, Via Sommarive 18, I-38050 Povo, Trento, Italy.
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56
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Heuck AP, Tweten RK, Johnson AE. Beta-barrel pore-forming toxins: intriguing dimorphic proteins. Biochemistry 2001; 40:9065-73. [PMID: 11478872 DOI: 10.1021/bi0155394] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- A P Heuck
- Department of Medical Biochemistry and Genetics, Texas A&M University System Health Science Center, College Station, Texas 77843-1114, USA
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57
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Affiliation(s)
- G Prévost
- Institut de Bactériologie de la Faculté de Médecine, Université Louis Pasteur-Hôpitaux Universitaires de Strasbourg, 3, rue Koeberlé, 67000 Strasbourg, France
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58
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Valeva A, Schnabel R, Walev I, Boukhallouk F, Bhakdi S, Palmer M. Membrane insertion of the heptameric staphylococcal alpha-toxin pore. A domino-like structural transition that is allosterically modulated by the target cell membrane. J Biol Chem 2001; 276:14835-41. [PMID: 11279048 DOI: 10.1074/jbc.m100301200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Staphylococcal alpha-toxin forms heptameric pores on eukaryotic cells. After binding to the cell membrane in its monomeric form, the toxin first assembles into a heptameric pre-pore. Subsequently, the pre-pore transforms into the final pore by membrane insertion of an amphipathic beta-barrel, which comprises the "central loop" domains of all heptamer subunits. The process of membrane insertion was analyzed here using a set of functionally altered toxin mutants. The results show that insertion may be initiated within an individual protomer when its NH2 terminus activates its central loop. The activated state is then shared with the central loops of the residual heptamer subunits, which results in cooperative membrane penetration. This cooperation of the central loops commences while these are still remote from the lipid bilayer. Nevertheless, it is subject to modulation by the target membrane, which therefore acts across a distance much like an allosteric effector. However, while allosteric transitions usually are reversible, membrane insertion of alpha-toxin is an irreversible event, and we show here that it can proceed to completion in a domino-like fashion when triggered by as little as a single foreign atom within the entire heptamer.
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Affiliation(s)
- A Valeva
- Institute of Medical Microbiology and Hygiene, University of Mainz, Obere Zahlbacher Strasse 67, D55101 Mainz, Germany.
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59
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Rose F, Zeller SA, Chakraborty T, Domann E, Machleidt T, Kronke M, Seeger W, Grimminger F, Sibelius U. Human endothelial cell activation and mediator release in response to Listeria monocytogenes virulence factors. Infect Immun 2001; 69:897-905. [PMID: 11159983 PMCID: PMC97967 DOI: 10.1128/iai.69.2.897-905.2001] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2000] [Accepted: 11/15/2000] [Indexed: 11/20/2022] Open
Abstract
The interaction of Listeria monocytogenes with endothelial cells represents a crucial step in the pathogenesis of listeriosis. Incubation of human umbilical vein endothelial cells (HUVEC) with wild-type L. monocytogenes (EGD) provoked immediate strong NO synthesis, attributable to listerial presentation of listeriolysin O (LLO), as the NO release was missed upon employment of a deletion mutant for LLO (EGD hly mutant) and was reproduced by purified LLO. Studies of conditions lacking extracellular Ca(2+) suggested LLO-elicited Ca(2+) flux as the underlying mechanism. In addition, HUVEC incubation with EGD turned out to be a potent stimulus for sustained (>12-h) upregulation of proinflammatory cytokine generation (interleukin 6 [IL-6], IL-8, and granulocyte-macrophage colony-stimulating factor). Use of deletion mutants for LLO (EGD hly mutant), listerial phosphatidylinositol-specific phospholipase C (EGD plcA mutant), broad-spectrum phospholipase C (EGD plcB mutant) and internalin B (EGD inlB mutant), as well as purified LLO, identified LLO as largely responsible for the cytokine response. Endothelial cells responded with diacylglycerole and ceramide generation as well as nuclear translocation of NF-kappa B to the stimulation with the LLO-producing strains EGD and Listeria innocua. The endothelial PC-phospholipase C inhibitor tricyclodecan-9-yl-xanthogenate as well as two independent inhibitors of NF-kappa B activation, pyrolidine dithiocarbamate and caffeic acid phenethyl ester, suppressed both the NF-kappa B translocation and the upregulation of cytokine synthesis. We conclude that L. monocytogenes is a potent stimulus of NO release and sustained upregulation of proinflammatory cytokine synthesis in human endothelial cells, both events being largely attributable to LLO presentation. LLO-induced transmembrane Ca(2+) flux as well as a sequence of endothelial phospholipase activation and the appearance of diacylglycerole, ceramide, and NF-kappa B are suggested as underlying host signaling events. These endothelial responses to L. monocytogenes may well contribute to the pathogenic sequelae in severe listerial infection and sepsis.
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Affiliation(s)
- F Rose
- Department of Internal Medicine, Justus Liebig University, Giessen, Germany
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60
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61
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Pédelacq JD, Prévost G, Monteil H, Mourey L, Samama JP. Crystal structure of the F component of the Panton-Valentine leucocidin. Int J Med Microbiol 2000; 290:395-401. [PMID: 11111917 DOI: 10.1016/s1438-4221(00)80050-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Leucocidins and gamma-hemolysins are bi-component staphylococcal toxins that form lytic transmembrane pores. Their cytotoxic activities involve the synergistic association of a class S and a class F component, produced as water-soluble monomers which assemble on the surface of specific cells. The structure of the F protein from Panton-Valentine leucocidin, solved at 2.0 A resolution, and sequence alignment suggest that it represents the fold of any secreted protein in this family of toxins. The comparison of this structure to that of the homoheptameric alpha-hemolysin provides some insights into the molecular events that may occur during pore formation.
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Affiliation(s)
- J D Pédelacq
- Groupe de Cristallographie Biologique, Institut de Pharmacologie et de Biologie Structurale du CNRS, Toulouse, France
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62
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Valeva A, Walev I, Gerber A, Klein J, Palmer M, Bhakdi S. Staphylococcal alpha-toxin: repair of a calcium-impermeable pore in the target cell membrane. Mol Microbiol 2000; 36:467-76. [PMID: 10792732 DOI: 10.1046/j.1365-2958.2000.01865.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Staphylococcal alpha-toxin forms heptameric pores that render membranes permeable for monovalent cations. The pore is formed by an amphipathic beta-barrel encompassing amino acid residues 118-140 of each subunit of the oligomer. Human fibroblasts are susceptible to alpha-toxin but are able to repair the membrane lesions. Thereby, toxin oligomers remain embedded in the plasma membrane and exposed to the extracellular medium. In this study, we sought to detect structural changes occurring in the pore-forming sequence during lesion repair. Single cysteine substitution mutants were labelled with the environmentally sensitive fluorochrome acrylodan and, after mixing with wild-type toxin, incorporated into hybrid heptamers on fibroblast membranes. Formation of the lipid-inserted beta-barrel was accompanied by characteristic fluorescence emission shifts. After lesion repair, the environment of the residues at the outer surface of the beta-barrel remained unchanged, indicating continued contact with lipids. However, the labelled residues oriented towards the channel lumen underwent a green to blue shift in fluorescence, indicating reduced exposure to water. Pore closure proceeded in the presence of calmodulin inhibitors and of microtubule disruptors; however, it was prevented by cytochalasin D and by inhibitors of lipid metabolism. Our findings reveal the existence of a novel mechanism of membrane repair that may consist in constriction of the inserted proteinaceous pore within the lipid bilayer.
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Affiliation(s)
- A Valeva
- Institutes of Medical Microbiology and Hygiene, and Pharmacology, University of Mainz, Hochhaus am Augustusplatz, D-55101 Mainz, Germany.
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63
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Abstract
This article reviews the literature regarding the structure and function of two types of exotoxins expressed by Staphylococcus aureus, pyrogenic toxin superantigens (PTSAgs) and hemolysins. The molecular basis of PTSAg toxicity is presented in the context of two diseases known to be caused by these exotoxins: toxic shock syndrome and staphylococcal food poisoning. The family of staphylococcal PTSAgs presently includes toxic shock syndrome toxin-1 (TSST-1) and most of the staphylococcal enterotoxins (SEs) (SEA, SEB, SEC, SED, SEE, SEG, and SEH). As the name implies, the PTSAgs are multifunctional proteins that invariably exhibit lethal activity, pyrogenicity, superantigenicity, and the capacity to induce lethal hypersensitivity to endotoxin. Other properties exhibited by one or more staphylococcal PTSAgs include emetic activity (SEs) and penetration across mucosal barriers (TSST-1). A detailed review of the molecular mechanisms underlying the toxicity of the staphylococcal hemolysins is also presented.
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64
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Dinges MM, Orwin PM, Schlievert PM. Exotoxins of Staphylococcus aureus. Clin Microbiol Rev 2000; 13:16-34, table of contents. [PMID: 10627489 PMCID: PMC88931 DOI: 10.1128/cmr.13.1.16] [Citation(s) in RCA: 743] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This article reviews the literature regarding the structure and function of two types of exotoxins expressed by Staphylococcus aureus, pyrogenic toxin superantigens (PTSAgs) and hemolysins. The molecular basis of PTSAg toxicity is presented in the context of two diseases known to be caused by these exotoxins: toxic shock syndrome and staphylococcal food poisoning. The family of staphylococcal PTSAgs presently includes toxic shock syndrome toxin-1 (TSST-1) and most of the staphylococcal enterotoxins (SEs) (SEA, SEB, SEC, SED, SEE, SEG, and SEH). As the name implies, the PTSAgs are multifunctional proteins that invariably exhibit lethal activity, pyrogenicity, superantigenicity, and the capacity to induce lethal hypersensitivity to endotoxin. Other properties exhibited by one or more staphylococcal PTSAgs include emetic activity (SEs) and penetration across mucosal barriers (TSST-1). A detailed review of the molecular mechanisms underlying the toxicity of the staphylococcal hemolysins is also presented.
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Affiliation(s)
- M M Dinges
- Department of Microbiology, University of Minnesota School of Medicine, Minneapolis, Minnesota 55455, USA
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65
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Browne KA, Blink E, Sutton VR, Froelich CJ, Jans DA, Trapani JA. Cytosolic delivery of granzyme B by bacterial toxins: evidence that endosomal disruption, in addition to transmembrane pore formation, is an important function of perforin. Mol Cell Biol 1999; 19:8604-15. [PMID: 10567584 PMCID: PMC84991 DOI: 10.1128/mcb.19.12.8604] [Citation(s) in RCA: 146] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Granule-mediated cell killing by cytotoxic lymphocytes requires the combined actions of a membranolytic protein, perforin, and granule-associated granzymes, but the mechanism by which they jointly kill cells is poorly understood. We have tested a series of membrane-disruptive agents including bacterial pore-forming toxins and hemolytic complement for their ability to replace perforin in facilitating granzyme B-mediated cell death. As with perforin, low concentrations of streptolysin O and pneumolysin (causing <10% (51)Cr release) permitted granzyme B-dependent apoptosis of Jurkat and Yac-1 cells, but staphylococcal alpha-toxin and complement were ineffective, regardless of concentration. The ensuing nuclear apoptotic damage was caspase dependent and included cleavage of poly(ADP-ribose) polymerase, suggesting a mode of action similar to that of perforin. The plasma membrane lesions formed at low dose by perforin, pneumolysin, and streptolysin did not permit diffusion of fluorescein-labeled proteins as small as 8 kDa into the cell, indicating that large membrane defects are not necessary for granzymes (32 to 65 kDa) to enter the cytosol and induce apoptosis. The endosomolytic toxin, listeriolysin O, also effected granzyme B-mediated cell death at concentrations which produced no appreciable cell membrane damage. Cells pretreated with inhibitors of endosomal trafficking such as brefeldin A took up granzyme B normally but demonstrated seriously impaired nuclear targeting of granzyme B when perforin was also added, indicating that an important role of perforin is to disrupt vesicular protein trafficking. Surprisingly, cells exposed to granzyme B with perforin concentrations that produced nearly maximal (51)Cr release (1,600 U/ml) also underwent apoptosis despite excluding a 8-kDa fluorescein-labeled protein marker. Only at concentrations of >4,000 U/ml were perforin pores demonstrably large enough to account for transmembrane diffusion of granzyme B. We conclude that pore formation may allow granzyme B direct cytosolic access only when perforin is delivered at very high concentrations, while perforin's ability to disrupt endosomal trafficking may be crucial when it is present at lower concentrations or in killing cells that efficiently repair perforin pores.
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Affiliation(s)
- K A Browne
- The Austin Research Institute, Heidelberg, Victoria 3084, Australia
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66
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Pédelacq JD, Maveyraud L, Prévost G, Baba-Moussa L, González A, Courcelle E, Shepard W, Monteil H, Samama JP, Mourey L. The structure of a Staphylococcus aureus leucocidin component (LukF-PV) reveals the fold of the water-soluble species of a family of transmembrane pore-forming toxins. Structure 1999; 7:277-87. [PMID: 10368297 DOI: 10.1016/s0969-2126(99)80038-0] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
BACKGROUND Leucocidins and gamma-hemolysins are bi-component toxins secreted by Staphylococcus aureus. These toxins activate responses of specific cells and form lethal transmembrane pores. Their leucotoxic and hemolytic activities involve the sequential binding and the synergistic association of a class S and a class F component, which form hetero-oligomeric complexes. The components of each protein class are produced as non-associated, water-soluble proteins that undergo conformational changes and oligomerization after recognition of their cell targets. RESULTS The crystal structure of the monomeric water-soluble form of the F component of Panton-Valentine leucocidin (LukF-PV) has been solved by the multiwavelength anomalous dispersion (MAD) method and refined at 2.0 A resolution. The core of this three-domain protein is similar to that of alpha-hemolysin, but significant differences occur in regions that may be involved in the mechanism of pore formation. The glycine-rich stem, which undergoes a major rearrangement in this process, forms an additional domain in LukF-PV. The fold of this domain is similar to that of the neurotoxins and cardiotoxins from snake venom. CONCLUSIONS The structure analysis and a multiple sequence alignment of all toxic components, suggest that LukF-PV represents the fold of any water-soluble secreted protein in this family of transmembrane pore-forming toxins. The comparison of the structures of LukF-PV and alpha-hemolysin provides some insights into the mechanism of transmembrane pore formation for the bi-component toxins, which may diverge from that of the alpha-hemolysin heptamer.
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Affiliation(s)
- J D Pédelacq
- Groupe de Cristallographie Biologique Institut de Pharmacologie et de Biologie Structurale du CNRS 205 route de Narbonne 31077 Toulouse Cedex France
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67
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Gouaux E. alpha-Hemolysin from Staphylococcus aureus: an archetype of beta-barrel, channel-forming toxins. J Struct Biol 1998; 121:110-22. [PMID: 9615434 DOI: 10.1006/jsbi.1998.3959] [Citation(s) in RCA: 196] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
alpha-Hemolysin, secreted from Staphylococcus aureus as a water-soluble monomer of 33.2 kDa, assembles on cell membranes to form transmembrane, heptameric channels. The structure of the detergent-solubilized heptamer has been determined by X-ray crystallography to 1.9 A resolution. The heptamer has a mushroom-like shape and measures up to 100 A in diameter and 100 A in height. Spanning the length of the molecule and coincident with the molecular sevenfold axis is a water-filled channel that ranges in diameter from approximately 16 to approximately 46 A. A 14 strand antiparallel beta-barrel, in which two strands are contributed by each subunit, defines the transmembrane domain. On the exterior of the beta-barrel there is a hydrophobic belt approximately 30 A in width that provides a surface complementary to the nonpolar portion of the lipid bilayer. The extensive promoter-protomer interfaces are composed of both salt-links and hydrogen bonds, as well as hydrophobic interactions, and these contacts provide a molecular rationalization for the stability of the heptamer in SDS solutions up to 65 degrees C. With the structure of the heptamer in hand, we can better understand the mechanisms by which the assembled protein interacts with the membrane and can postulate mechanisms of assembly.
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Affiliation(s)
- E Gouaux
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA
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68
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Palmer M, Harris R, Freytag C, Kehoe M, Tranum-Jensen J, Bhakdi S. Assembly mechanism of the oligomeric streptolysin O pore: the early membrane lesion is lined by a free edge of the lipid membrane and is extended gradually during oligomerization. EMBO J 1998; 17:1598-605. [PMID: 9501081 PMCID: PMC1170507 DOI: 10.1093/emboj/17.6.1598] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Streptolysin O (SLO) is a bacterial exotoxin that binds to cell membranes containing cholesterol and then oligomerizes to form large pores. Along with rings, arc-shaped oligomers form on membranes. It has been suggested that each arc represents an incompletely assembled oligomer and constitutes a functional pore, faced on the opposite side by a free edge of the lipid membrane. We sought functional evidence in support of this idea by using an oligomerization-deficient, non-lytic mutant of SLO. This protein, which was created by chemical modification of a single mutant cysteine (T250C) with N-(iodoacetaminoethyl)-1-naphthylamine-5-sulfonic acid, formed hybrid oligomers with active SLO on membranes. However, incorporation of the modified T250C mutant inhibited subsequent oligomerization, so that the hybrid oligomers were reduced in size. These appeared as typical arc lesions in the electron microscope. They formed pores that permitted passage of NaCl and calcein but restricted permeation of large dextran molecules. The data indicate that the SLO pore is formed gradually during oligomerization, implying that pores lined by protein on one side and an edge of free lipid on the other may be created in the plasma membrane. Intentional manipulation of the pore size may extend the utility of SLO as a tool in cell biological experiments.
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Affiliation(s)
- M Palmer
- Institute of Medical Microbiology, University of Mainz, Augustusplatz, D-55101 Mainz, Germany
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