Abstract
Staphylococcus aureus exhibits a myriad of virulence elements, including β-barrel pore-forming toxins (β-PFTs). The primary mission of these protein toxins is to destroy the physical and chemical gradients across the membrane of the targeted cell by generating well-defined transmembrane pores, ultimately causing the cell death. Such a form of biomolecular attack is a ubiquitous membrane-perforation mechanism in numerous organisms, including bacterial systems and eukaryotes. One unusual commonality of the β-PFTs is their amphipathic nature, enabling sophisticated conformational alterations that are required for their transit from the secreting to attacked cell. Intriguingly enough, proteinaceous toxins are secreted as a hydrophilic form. Then, they must navigate within the aqueous phase between the two cells and ultimately breach the hydrophobic barrier posed by the susceptible cell membrane. The archetype of these non-enzymatic staphylococcal β-PFTs is the homoheptameric α-hemolysin (αHL) protein. Moreover, S. aureus has the ability to secrete up to four heteromeric, bi-component β-PFTs. Although the homomeric and heteromeric β-PFTs are related in sequence, homology, and structure, they demonstrate distinct biophysical features.
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References
Akeson M, Branton D, Kasianowicz JJ, Brandin E, Deamer DW (1999) Microsecond time-scale discrimination among polycytidylic acid, polyadenylic acid, and polyuridylic acid as homopolymers or as segments within single RNA molecules. Biophys J 77:3227–3233
Aksimentiev A, Schulten K (2005) Imaging {alpha}-Hemolysin with Molecular Dynamics: Ionic Conductance, Osmotic Permeability, and the Electrostatic Potential Map. Biophys J 88:3745–3761
Alonzo F III, Torres VJ (2014) The bicomponent pore-forming leucocidins of Staphylococcus aureus. Microbiol Mol Biol Rev 78:199–230
Astier Y, Bayley H, Howorka S (2005) Protein components for nanodevices. Curr Opin Chem Biol 9:576–584
Baaken G, Ankri N, Schuler AK, Ruhe J, Behrends JC (2011) Nanopore-based single-molecule mass spectrometry on a lipid membrane microarray. ACS Nano 5:8080–8088
Balijepalli A, Ettedgui J, Cornio AT, Robertson JW, Cheung KP, Kasianowicz JJ, Vaz C (2014) Quantifying short-lived events in multistate ionic current measurements. ACS Nano 8:1547–1553
Bayley H (2006) Sequencing single molecules of DNA. Curr Opin Chem Biol 10:628–637
Bayley H, Braha O, Cheley S, Gu LQ (2004) Engineered nanopores. In: Mirkin CA, Niemeyer CM (eds) NanoBiotechnology. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, pp 93–112
Bayley H, Cremer PS (2001) Stochastic sensors inspired by biology. Nature 413:226–230
Bayley H, Jayasinghe L (2004) Functional engineered channels and pores (review). Mol Membr Biol 21:209–220
Benner S, Chen RJ, Wilson NA, Abu-Shumays R, Hurt N, Lieberman KR, Deamer DW, Dunbar WB, Akeson M (2007) Sequence-specific detection of individual DNA polymerase complexes in real time using a nanopore. Nat Nanotechnol 2:718–724
Bezrukov SM (2000) Ion channels as molecular Coulter counters to probe metabolite transport. J Membr Biol 174:1–13
Bezrukov SM, Kasianowicz JJ (1993) Current noise reveals protonation kinetics and number of ionizable sites in an open protein ion channel. Phys Rev Lett 70:2352–2355
Bezrukov SM, Krasilnikov OV, Yuldasheva LN, Berezhkovskii AM, Rodrigues CG (2004) Field-Dependent Effect of Crown Ether (18-Crown-6) on Ionic Conductance of {alpha}-Hemolysin Channels. Biophys J 87:3162–3171
Bezrukov SM, Vodyanoy I, Brutyan RA, Kasianowicz JJ (1996) Dynamics and free energy of polymers partitioning into a nanoscale pore. Macromolecules 29:8517–8522
Bischofberger M, Gonzalez MR, van der Goot FG (2009) Membrane injury by pore-forming proteins. Curr Opin Cell Biol 21:589–595
Braha O, Walker B, Cheley S, Kasianowicz JJ, Song LZ, Gouaux JE, Bayley H (1997) Designed protein pores as components for biosensors. Chem Biol 4:497–505
Branton D, Deamer DW, Marziali A, Bayley H, Benner SA, Butler T, Di Ventra M, Garaj S, Hibbs A, Huang X, Jovanovich SB, Krstic PS, Lindsay S, Ling XS, Mastrangelo CH, Meller A, Oliver JS, Pershin YV, Ramsey JM, Riehn R, Soni GV, Tabard-Cossa V, Wanunu M, Wiggin M, Schloss JA (2008) The potential and challenges of nanopore sequencing. Nat Biotechnol 26:1146–1153
Brochard-Wyart F, De Gennes P-G, Sandre O (2000) Transient pores in stretched vesicles: role of leak-out. Physica A 278:32–51
Cheley S, Malghani MS, Song LZ, Hobaugh M, Gouaux JE, Yang J, Bayley H (1997) Spontaneous oligomerization of a staphylococcal alpha-hemolysin conformationally constrained by removal of residues that form the transmembrane beta-barrel. Protein Eng 10:1433–1443
Cherf GM, Lieberman KR, Rashid H, Lam CE, Karplus K, Akeson M (2012) Automated forward and reverse ratcheting of DNA in a nanopore at 5-A precision. Nat Biotechnol 30:344–348
Comai M, Serra MD, Coraiola M, Werner S, Colin DA, Monteil H, Prevost G, Menestrina G (2002) Protein engineering modulates the transport properties and ion selectivity of the pores formed by staphylococcal gamma- haemolysins in lipid membranes. Molecular Microbiology 44:1251–1267
Czajkowsky DM, Sheng ST, Shao ZF (1998) Staphylococcal alpha-hemolysin can form hexamers in phospholipid bilayers. J Mol Biol 276:325–330
De Gennes P-G (1999a) Flexible polymers in nanopores. Adv Polym Sci 138:91–105
De Gennes P-G (1999b) Passive entry of a DNA molecule into a small pore. Proc Natl Acad Sci U S A 96:7262–7264
De Gennes P-G (1999c) Problems of DNA entry into a cell. Physica A 274:1–7
DuMont AL, Torres VJ (2014) Cell targeting by the Staphylococcus aureus pore-forming toxins: it’s not just about lipids. Trends Microbiol 22:21–27
Fang Y, Cheley S, Bayley H, Yang J (1997) The heptameric prepore of a Staphylococcal alpha-hemolysin mutant in lipid bilayers imaged by atomic force microscopy. Biochemistry 36:9518–9522
Ferreras M, Hoper F, Dalla Serra M, Colin DA, Prevost G, Menestrina G (1998) The interaction of Staphylococcus aureus bi-component gamma- hemolysins and leucocidins with cells and lipid membranes. Biochim Biophys Acta -Biomembr 1414:108–126
Gonzalez MR, Bischofberger M, Pernot L, van der Goot FG, Freche B (2008) Bacterial pore-forming toxins: the (w)hole story? Cell Mol Life Sci 65:493–507
Goodrich CP, Kirmizialtin S, Huyghues-Despointes BM, Zhu AP, Scholtz JM, Makarov DE, Movileanu L (2007) Single-molecule electrophoresis of beta-hairpin peptides by electrical recordings and Langevin dynamics simulations. J Phys Chem B 111:3332–3335
Gouaux E (1998) Alpha-hemolysin from staphylococcus aureus: an archetype of beta-barrel, channel-forming toxins. J Struct Biol 121:110–122
Gouaux E, Hobaugh M, Song LZ (1997) Alpha-hemolysin, gamma-hemolysin, and leukocidin from staphylococcus aureus: distant in sequence but similar in structure. Protein Sci 6:2631–2635
Gouaux JE, Braha O, Hobaugh MR, Song LZ, Cheley S, Shustak C, Bayley H (1994) Subunit stoichiometry of staphylococcal Alfa-hemolysin in crystals and on membranes - a heptameric transmembrane pore. Proc Natl Acad Sci U S A 91:12828–12831
Gu LQ, Bayley H (2000) Interaction of the noncovalent molecular adapter, beta- cyclodextrin, with the staphylococcal alpha-hemolysin pore. Biophys J 79:1967–1975
Gu LQ, Braha O, Conlan S, Cheley S, Bayley H (1999) Stochastic sensing of organic analytes by a pore-forming protein containing a molecular adapter. Nature 398:686–690
Gu LQ, Cheley S, Bayley H (2003) Electroosmotic enhancement of the binding of a neutral molecule to a transmembrane pore. Proc Natl Acad Sci U S A 100:15498–15503
Guillet V, Roblin P, Werner S, Coraiola M, Menestrina G, Monteil H, Prevost G, Mourey L (2004) Crystal structure of leucotoxin S component: new insight into the Staphylococcal beta-barrel pore-forming toxins. J Biol Chem 279:41028–41037
Gurnev PA, Nestorovich EM (2014) Channel-forming bacterial toxins in biosensing and macromolecule delivery. Toxins (Basel) 6:2483–2540
Hall AR, Scott A, Rotem D, Mehta KK, Bayley H, Dekker C (2010) Hybrid pore formation by directed insertion of alpha-haemolysin into solid-state nanopores. Nat Nanotechnol 5:874–877
Heuck AP, Tweten RK, Johnson AE (2001) Beta-Barrel pore-forming toxins: intriguing dimorphic proteins. Biochemistry 40:9065–9073
Holden MA, Jayasinghe L, Daltrop O, Mason A, Bayley H (2006) Direct transfer of membrane proteins from bacteria to planar bilayers for rapid screening by single-channel recording. Nat Chem Biol 2:314–318
Hornblower B, Coombs A, Whitaker RD, Kolomeisky A, Picone SJ, Meller A, Akeson M (2007) Single-molecule analysis of DNA-protein complexes using nanopores. Nat Methods 4:315–317
Howorka S, Movileanu L, Lu XF, Magnon M, Cheley S, Braha O, Bayley H (2000) A protein pore with a single polymer chain tethered within the lumen. J Am Chem Soc 122:2411–2416
Howorka S, Siwy Z (2008) Nanopores: generation, engineering and single-molecule applications. In: Hinterdorfer P (ed) Handbook of single-molecule biophysics. Springer, New York
Howorka S, Siwy Z (2009) Nanopore analytics: sensing of single molecules. Chem Soc Rev 38:2360–2384
Iacovache I, Bischofberger M, van der Goot FG (2010) Structure and assembly of pore-forming proteins. Curr Opin Struct Biol 20:241–246
Iacovache I, van der Goot FG, Pernot L (2008) Pore formation: an ancient yet complex form of attack. Biochim Biophys Acta 1778:1611–1623
Jayasinghe L, Bayley H (2005) The leukocidin pore: evidence for an octamer with four LukF subunits and four LukS subunits alternating around a central axis. Protein Sci 14:2550–2561
Jung Y, Bayley H, Movileanu L (2006) Temperature-responsive protein pores. J Am Chem Soc 128:15332–15340
Kang XF, Gu LQ, Cheley S, Bayley H (2005) Single protein pores containing molecular adapters at high temperatures. Angew Chem Int Ed Engl 44:1495–1499
Kasianowicz JJ, Bezrukov SM (1995) Protonation dynamics of the alpha-toxin ion-channel from spectral-analysis of ph-dependent current fluctuations. Biophys J 69:94–105
Kasianowicz JJ, Brandin E, Branton D, Deamer DW (1996) Characterization of individual polynucleotide molecules using a membrane channel. Proc Natl Acad Sci U S A 93:13770–13773
Kolomeisky AB (2007) Channel-facilitated molecular transport across membranes: attraction, repulsion, and asymmetry. Phys Rev Lett 98:048105
Kolomeisky AB (2008) How polymers translocate through pores: memory is important. Biophys J 94:1547–1548
Kong CY, Muthukumar M (2005) Simulations of stochastic sensing of proteins. J Am Chem Soc 127:18252–18261
Korchev YE, Alder GM, Bakhramov A, Bashford CL, Joomun BS, Sviderskaya EV, Usherwood PN, Pasternak CA (1995) Staphylococcus aureus alpha-toxin-induced pores: channel-like behavior in lipid bilayers and patch clamped cells. J Membr Biol 143:143–151
Krasilnikov OV, Bezrukov SM (2004) Polymer partitioning from nonideal solutions into protein voids. Macromolecules 37:2650–2657
Krasilnikov OV, Merzlyak PG, Yuldasheva LN, Rodrigues CG, Bhakdi S, Valeva A (2000) Electrophysiological evidence for heptameric stoichiometry of ion channels formed by Staphylococcus aureus alpha-toxin in planar lipid bilayers. Molecular Microbiology 37:1372–1378
Krasilnikov OV, Rodrigues CG, Bezrukov SM (2006) Single polymer molecules in a protein nanopore in the limit of a strong polymer-pore attraction. Phys Rev Lett 97:018301
Kusters I, van Oijen AM, Driessen AJ (2014) Membrane-on-a-chip: microstructured silicon/silicon-dioxide chips for high-throughput screening of membrane transport and viral membrane fusion. ACS Nano 8:3380–3392
Los FC, Randis TM, Aroian RV, Ratner AJ (2013) Role of pore-forming toxins in bacterial infectious diseases. Microbiol Mol Biol Rev 77:173–207
Maffeo C, Bhattacharya S, Yoo J, Wells D, Aksimentiev A (2012) Modeling and simulation of ion channels. Chem Rev 112:6250–6284
Maglia G, Heron AJ, Hwang WL, Holden MA, Mikhailova E, Li Q, Cheley S, Bayley H (2009) Droplet networks with incorporated protein diodes show collective properties. Nat Nanotechnol 4:437–440
Maglia G, Restrepo MR, Mikhailova E, Bayley H (2008) Enhanced translocation of single DNA molecules through {alpha}-hemolysin nanopores by manipulation of internal charge. Proc Natl Acad Sci U S A 105:19720–19725
Majd S, Yusko EC, Billeh YN, Macrae MX, Yang J, Mayer M (2010) Applications of biological pores in nanomedicine, sensing, and nanoelectronics. Curr Opin Biotechnol 21:439–476
Mayer M, Yang J (2013) Engineered ion channels as emerging tools for chemical biology. Acc Chem Res 46:2998–3008
Meller A, Nivon L, Brandin E, Golovchenko J, Branton D (2000) Rapid nanopore discrimination between single polynucleotide molecules. Proc Natl Acad Sci U S A 97:1079–1084
Menestrina G (1986) Ionic channels formed by staphylococcus-aureus alpha-toxin – voltage-dependent inhibition by divalent and trivalent cations. J Membr Biol 90:177–190
Menestrina G, Dalla Serra M, Prevost G (2001) Mode of action of beta-barrel pore-forming toxins of the staphylococcal alpha-hemolysin family. Toxicon 39:1661–1672
Menestrina G, Dalla SM, Comai M, Coraiola M, Viero G, Werner S, Colin DA, Monteil H, Prevost G (2003) Ion channels and bacterial infection: the case of beta-barrel pore-forming protein toxins of Staphylococcus aureus. FEBS Lett 552:54–60
Miles G, Bayley H, Cheley S (2002a) Properties of Bacillus cereus hemolysin II: a heptameric transmembrane pore. Protein Sci 11:1813–1824
Miles G, Cheley S, Braha O, Bayley H (2001) The staphylococcal leukocidin bicomponent toxin forms large ionic channels. Biochemistry 40:8514–8522
Miles G, Movileanu L, Bayley H (2002b) Subunit composition of a bicomponent toxin: staphylococcal leukocidin forms an octameric transmembrane pore. Protein Sci 11:894–902
Misakian M, Kasianowicz JJ (2003) Electrostatic influence on ion transport through the alphaHL channel. J Membr Biol 195:137–146
Mohammad MM, Iyer R, Howard KR, McPike MP, Borer PN, Movileanu L (2012) Engineering a rigid protein tunnel for biomolecular detection. J Am Chem Soc 134:9521–9531
Mohammad MM, Movileanu L (2010) Impact of distant charge reversals within a robust beta-barrel protein pore. J Phys Chem B 114:8750–8759
Montoya M, Gouaux E (2003) Beta-barrel membrane protein folding and structure viewed through the lens of alpha-hemolysin. Biochim Biophys Acta 1609:19–27
Movileanu L (2008) Squeezing a single polypeptide through a nanopore. Soft Matter 4:925–931
Movileanu L (2009) Interrogating single proteins through nanopores: challenges and opportunities. Trends Biotechnol 27:333–341
Movileanu L, Bayley H (2001) Partitioning of a polymer into a nanoscopic protein pore obeys a simple scaling law. Proc Natl Acad Sci U S A 98:10137–10141
Movileanu L, Cheley S, Bayley H (2003) Partitioning of individual flexible polymers into a nanoscopic protein pore. Biophys J 85:897–910
Movileanu L, Cheley S, Howorka S, Braha O, Bayley H (2001) Location of a constriction in the lumen of a transmembrane pore by targeted covalent attachment of polymer molecules. J Gen Physiol 117:239–251
Movileanu L, Howorka S, Braha O, Bayley H (2000) Detecting protein analytes that modulate transmembrane movement of a polymer chain within a single protein pore. Nat Biotechnol 18:1091–1095
Movileanu L, Schmittschmitt JP, Scholtz JM, Bayley H (2005) Interactions of the peptides with a protein pore. Biophys J 89:1030–1045
Muthukumar M (1999) Polymer translocation through a hole. J Chem Phys 111:10371–10374
Muthukumar M (2007) Mechanism of DNA transport through pores. Annu Rev Biophys Biomol Struct 36:435–450
Nivala J, Marks DB, Akeson M (2013) Unfoldase-mediated protein translocation through an alpha-hemolysin nanopore. Nat Biotechnol 31:247–250
Noskov SY, Im W, Roux B (2004) Ion permeation through the alpha-hemolysin channel: theoretical studies based on Brownian dynamics and Poisson-Nernst-Plank electrodiffusion theory. Biophys J 87:2299–2309
Olson R, Nariya H, Yokota K, Kamio Y, Gouaux E (1999) Crystal structure of Staphylococcal LukF delineates conformational changes accompanying formation of a transmembrane channel. Nat Struct Biol 6:134–140
Otto M (2014) Staphylococcus aureus toxins. Curr Opin Microbiol 17:32–37
Parker MW, Feil SC (2005) Pore-forming protein toxins: from structure to function. Prog Biophys Mol Biol 88:91–142
Pedelacq JD, Maveyraud L, Prevost G, Baba-Moussa L, Gonzalez A, Courcelle E, Shepard W, Monteil H, Samama JP, Mourey L (1999) 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 7:277–287
Potrich C, Bastiani H, Colin DA, Huck S, Prevost G, Dalla SM (2009) The influence of membrane lipids in Staphylococcus aureus gamma-hemolysins pore formation. J Membr Biol 227:13–24
Prevost G, Mourey L, Colin DA, Menestrina G (2001) Staphylococcal pore-forming toxins. Pore-Forming Toxins 257:53–83
Reiner JE, Kasianowicz JJ, Nablo BJ, Robertson JW (2010) Theory for polymer analysis using nanopore-based single-molecule mass spectrometry. Proc Natl Acad Sci U S A 107:12080–12085
Robertson JW, Kasianowicz JJ, Reiner JE (2010) Changes in ion channel geometry resolved to sub-angstrom precision via single molecule mass spectrometry. J Phys Condens Matter 22:454108
Robertson JW, Rodrigues CG, Stanford VM, Rubinson KA, Krasilnikov OV, Kasianowicz JJ (2007) Single-molecule mass spectrometry in solution using a solitary nanopore. Proc Natl Acad Sci U S A 104:8207–8211
Rodrigues CG, Machado DC, Chevtchenko SF, Krasilnikov OV (2008) Mechanism of KCl enhancement in detection of nonionic polymers by nanopore sensors. Biophys J 95:5186–5192
Rodriguez-Larrea D, Bayley H (2013) Multistep protein unfolding during nanopore translocation. Nat Nanotechnol 8:288–295
Sackmann B, Neher E (1995) Single-channel recording. Kluwer Academic/Plenum Publishers, New York
Sanchez-Quesada J, Ghadiri MR, Bayley H, Braha O (2000) Cyclic peptides as molecular adapters for a pore-forming protein. J Am Chem Soc 122:11757–11766
Siwy ZS, Howorka S (2010) Engineered voltage-responsive nanopores. Chem Soc Rev 39:1115–1132
Slonkina E, Kolomeisky AB (2003) Polymer translocation through a long nanopore. J Chem Phys 118:7112–7118
Song LZ, Hobaugh MR, Shustak C, Cheley S, Bayley H, Gouaux JE (1996) Structure of staphylococcal alpha-hemolysin, a heptameric transmembrane pore. Science 274:1859–1866
Sugawara-Tomita N, Tomita T, Kamio Y (2002) Stochastic assembly of two-component staphylococcal gamma- hemolysin into heteroheptameric transmembrane pores with alternate subunit arrangements in ratios of 3: 4 and 4: 3. J Bacteriol 184:4747–4756
Sutherland TC, Long YT, Stefureac RI, Bediako-Amoa I, Kraatz HB, Lee JS (2005) Structure of peptides investigated by nanopore analysis. Nano Lett 4:1273–1277
Tian P, Andricioaei I (2005) Repetitive pulling catalyzes co-translocational unfolding of barnase during import through a mitochondrial pore. J Mol Biol 350:1017–1034
Walker B, Bayley H (1995) Restoration of pore-forming activity in staphylococcal alfa-hemolysin by targeted covalent modification. Protein Eng 8:491–495
Wang HY, Gu Z, Cao C, Wang J, Long YT (2013a) Analysis of a single alpha-synuclein fibrillation by the Interaction with a Protein Nanopore. Anal Chem 85:8254–8261
Wang S, Haque F, Rychahou PG, Evers BM, Guo P (2013b) Engineered nanopore of Phi29 DNA-packaging motor for real-time detection of single colon cancer specific antibody in serum. ACS Nano 7:9814–9822
Wang Y, Zheng D, Tan Q, Wang MX, Gu LQ (2011) Nanopore-based detection of circulating microRNAs in lung cancer patients. Nat Nanotechnol 6:668–674
Wells DB, Abramkina V, Aksimentiev A (2007) Exploring transmembrane transport through alpha-hemolysin with grid-steered molecular dynamics. J Chem Phys 127:125101
Werner S, Colin DA, Coraiola M, Menestrina G, Monteil H, Prevost G (2002) 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 70:1310–1318
White SH, Wimley WC (1999) Membrane protein folding and stability: physical principles. Annu Rev Biophys Biomol Struct 28:319–365
Wimley WC (2003) The versatile beta-barrel membrane protein. Curr Opin Struct Biol 13:404–411
Yamashita K, Kawai Y, Tanaka Y, Hirano N, Kaneko J, Tomita N, Ohta M, Kamio Y, Yao M, Tanaka I (2011) Crystal structure of the octameric pore of staphylococcal gamma-hemolysin reveals the beta-barrel pore formation mechanism by two components. Proc Natl Acad Sci U S A 108:17314–17319
Yoong P, Torres VJ (2013) The effects of Staphylococcus aureus leukotoxins on the host: cell lysis and beyond. Curr Opin Microbiol 16:63–69
Acknowledgments
We are grateful to members of the Movileanu laboratory for their constructive comments. We realized the challenging nature of writing a chapter about a β-barrel toxin that has transformed the area of nanopore biophysics. Therefore, we regret that due to space limitations we were unable to introduce all exciting publications pertinent to this field. This work was supported by the National Institutes of Health, Grant GM088403 (to L.M.).
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Gugel, J.F., Movileanu, L. (2015). Staphylococcal β-barrel Pore-Forming Toxins: Mushrooms That Breach the Greasy Barrier. In: Delcour, A.H. (eds) Electrophysiology of Unconventional Channels and Pores. Springer Series in Biophysics, vol 18. Springer, Cham. https://doi.org/10.1007/978-3-319-20149-8_10
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