Pore Formation by S. aureus α-toxin in Liposomes and Planar Lipid Bilayers: Effects of Nonelectrolytes

Bashford, C. L.; Alder, G. M.; Fulford, L.G.; Korchev, Yuri; Kovacs, Elizabeth J.; Mackinnon, A.M.; Pederzolli, Cecilia; Pasternak, C. A.

doi:10.1007/s002329900028

Cited by 22 publications

(20 citation statements)

References 25 publications

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“…This could be due to the approach used for evaluating the time necessary to obtain 50% lysis. These values were underestimated in the presence of PEGs in standard solution 3 because in BLM experiments we observed, in agreement with [1], that PEGs induce an increase in the rate of channel formation by the toxin.…”

Section: Planar Blm Experimentssupporting

confidence: 85%

Pore-forming properties of proteolytically nicked staphylococcal ⋅-toxin: the ion channel in planar lipid bilayer membranes

Krasilnikov

Merzlyak

Yuldasheva

et al. 1997

Medical Microbiology and Immunology

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Staphylococcal alpha-toxin is a single-chain protein with a molecular mass of 33.2 kDa, which can form large water-filled pores both in lipid bilayers and in erythrocyte membranes. Limited proteolysis of the purified toxin with proteinase K led to time-dependent changes of all the functional features of the channels formed by the toxin. Single-channel conductance in planar bilayers was decreased about threefold. The anion selectivity of the channel was replaced with cation selectivity and the asymmetry in the current-voltage relationship of the channel became more pronounced. At the same time the nicked toxin kept its full ability to form ion channels in lipid bilayers, although it lost a considerable part of its hemolytic activity. In planar bilayers and in erythrocyte membranes, the proteolytically nicked toxin actually formed channels with a slightly smaller diameter (approximately 1.2 times) than that formed by the native toxin. This decrease was not marked enough to explain changes in the biological effects of the nicked toxin. The change in channel selectivity induced by the cleavage is considered to be the major determinant of the changes in the biological effects of the nicked toxin.

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Section: Planar Blm Experimentssupporting

confidence: 85%

Pore-forming properties of proteolytically nicked staphylococcal ⋅-toxin: the ion channel in planar lipid bilayer membranes

Krasilnikov

Merzlyak

Yuldasheva

et al. 1997

Medical Microbiology and Immunology

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“…The critical dependence of the hemolytic inhibition on the PEG molecular size permits us to discard a membrane permeabilization based on a detergent-like mechanism and also to estimate the size of the putative membrane pore (28), in this case ϳ1.2 nm. This is in good agreement with the sizes of pores created by aerolysin (44,45), ␣-hemolysin from Staphylococcus aureus (45,46), and ␣-toxin from Clostridium septicum (AT) (31).…”

Section: Hydralysins Are a Diverse Family Of Toxins In Hydrae-wesupporting

confidence: 78%

Hydralysins, a New Category of β-Pore-forming Toxins in Cnidaria

Sher¹,

Fishman²,

Zhang³

et al. 2005

Journal of Biological Chemistry

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Cnidaria are venomous animals that produce diverse protein and polypeptide toxins, stored and delivered into the prey through the stinging cells, the nematocytes. These include pore-forming cytolytic toxins such as well studied actinoporins. In this work, we have shown that the non-nematocystic paralytic toxins, hydralysins, from the green hydra Chlorohydra viridissima comprise a highly diverse group of ␤-pore-forming proteins, distinct from other cnidarian toxins but similar in activity and structure to bacterial and fungal toxins. Functional characterization of hydralysins reveals that as soluble monomers they are rich in ␤-structure, as revealed by far UV circular dichroism and computational analysis. Hydralysins bind erythrocyte membranes and form discrete pores with an internal diameter of ϳ1.2 nm. The cytolytic effect of hydralysin is cell type-selective, suggesting a specific receptor that is not a phospholipid or carbohydrate. Multiple sequence alignment reveals that hydralysins share a set of conserved sequence motifs with known pore-forming toxins such as aerolysin, ⑀-toxin, ␣-toxin, and LSL and that these sequence motifs are found in and around the poreforming domains of the toxins. The importance of these sequence motifs is revealed by the cloning, expression, and mutagenesis of three hydralysin isoforms that strongly differ in their hemolytic and paralytic activities. The correlation between the paralytic and cytolytic activities of hydralysin suggests that both are a consequence of receptor-mediated pore formation. Hydralysins and their homologues exemplify the wide distribution of ␤-pore formers in biology and provide a useful model for the study of their molecular mode of action.

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“…This is confirmed by the symmetrical voltage dependence exhibited by both the wtOEP16 and the mutant proteins. This voltage dependence of the open probability is also a characteristic feature of other reconstituted ␤-barrel pores like porins (36,37), ␤-CFTs (␤-barrel channel forming toxins) (38) and of the protein-translocation pores in the outer membranes of chloroplasts and mitochondria (26,27). It seems that this voltage dependence is not generated by special structures in the pore lumen, and it is consequently considered to be an intrinsic feature of the ␤-barrel (39).…”

Section: Discussionmentioning

confidence: 87%

Identification of the Pore-forming Region of the Outer Chloroplast Envelope Protein OEP16

Steinkamp¹,

Hill²,

Hinnah³

et al. 2000

Journal of Biological Chemistry

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The chloroplast outer envelope protein OEP16 forms a cation-selective high conductance channel with permeability to amines and amino acids. The region of OEP16 directly involved in channel formation has been identified by electrophysiological analysis of a selection of reconstituted OEP16 mutants. Because analysis of these mutants depended on the use of recombinant protein, we evaluated the electrophysiological properties of OEP16 isolated directly from pea chloroplasts and of the recombinant protein produced in Escherichia coli. The results show that the basic properties like conductance, selectivity, and open probability of the channel formed by native pea OEP16 are comparable with the channel activity formed by the recombinant source of the protein. Following electrophysiological analysis of OEP16 mutants we found that point mutations and insertion of additional amino acid residues in the region of the putative helix 1 (Glu 73 to Val 91 ) did not change the properties of the OEP16 channel. The only exception was a Cys 71 3 Ser mutation, which led to a loss of the CuCl 2 sensitivity of the channel. Analysis of N-and C-terminal deletion mutants of OEP16 and mutants containing defined shuffled domains indicated that the minimal continuous region of OEP16, which is able to form a channel in liposomes, lies in the first half of the protein between amino acid residues 21 and 93.The plastid organelle family conducts vital biosynthetic functions in every plant cell. Chloroplasts carry out photosynthesis, which converts atmospheric carbon dioxide to carbohydrates like triosephosphate, starch, and others. These and other biosynthetic pathway products and intermediates are steadily exchanged with the surrounding cell by the assistance of specific carrier proteins, localized in the plastidic inner envelope and solute channels located in the chloroplast outer envelope. Although the inner envelope transport proteins, such as the triosephosphate/phosphate translocator, the dicarboxylate translocator, and the hexose phosphate translocator, show distinct substrate selectivity and specificity (1), it is not known to what extent transport through the outer membrane channels is selective and regulated. In particular, the number of different channels present in the outer membrane has not been determined.In mitochondria, a single anion selective channel with high conductance (VDAC) 1 has been discovered and extensively characterized at a molecular level (2). A second protein with high homology to the VDAC channel has also been identified (3). The VDAC channel formed by a 30-kDa protein with presumed ␤-sheet topology (4) is thought to be responsible for most of the metabolite flux across the outer mitochondrial membrane (5).In Gram-negative bacteria, however, several different types of high conductance channels exist in the outer membrane (6): (i) So-called porins, forming water-filled pores that allow the downhill diffusion of solutes, provided that the size of the solutes does not exceed the exclusion limit (ϳ600 Da) of the chann...

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Pore Formation by S. aureus α-toxin in Liposomes and Planar Lipid Bilayers: Effects of Nonelectrolytes

Cited by 22 publications

References 25 publications

Pore-forming properties of proteolytically nicked staphylococcal ⋅-toxin: the ion channel in planar lipid bilayer membranes

Pore-forming properties of proteolytically nicked staphylococcal ⋅-toxin: the ion channel in planar lipid bilayer membranes

Hydralysins, a New Category of β-Pore-forming Toxins in Cnidaria

Identification of the Pore-forming Region of the Outer Chloroplast Envelope Protein OEP16

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