Molecular Architecture and Functional Analysis of NetB, a Pore-forming Toxin from Clostridium perfringens

Savva, Christos G.; Costa, Sérgio P. Fernandes da; Bokori-Brown, Monika; Naylor, C.E.; Cole, A.R.; Moss, David S.; Titball, Richard W.; Basak, A.K.

doi:10.1074/jbc.m112.430223

Cited by 99 publications

(141 citation statements)

References 41 publications

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“…Like most of these toxins, it is produced as a monomer and presumably oligomerizes on the host cell surface prior to membrane insertion, forming 1.6-to 1.8-nm pores in susceptible chicken leghorn male hepatoma (LMH) cells (11). The structures of both the soluble monomeric form of NetB (133) and a heptameric pore form of NetB (134) have recently been solved, and its structural similarity to S. aureus alpha-hemolysin was confirmed. Although the precise NetB receptor has not been identified, there is evidence for cell specificity, since not all chicken cell lines are susceptible to NetB (11).…”

Section: Plasmid-encoded Toxinsmentioning

confidence: 99%

“…Although the precise NetB receptor has not been identified, there is evidence for cell specificity, since not all chicken cell lines are susceptible to NetB (11). Recent studies have shown that NetB interacts with cholesterol to enhance pore formation (134) and that it formed pores with much higher single-channel conductance than alpha-hemolysin and varied in its ion selectivity, preferring cations over anions (133).…”

Section: Plasmid-encoded Toxinsmentioning

confidence: 99%

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Toxin Plasmids of Clostridium perfringens

Adams

Bannam

et al. 2013

Microbiol Mol Biol Rev

231

282

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SUMMARY In both humans and animals, Clostridium perfringens is an important cause of histotoxic infections and diseases originating in the intestines, such as enteritis and enterotoxemia. The virulence of this Gram-positive, anaerobic bacterium is heavily dependent upon its prolific toxin-producing ability. Many of the ∼16 toxins produced by C. perfringens are encoded by large plasmids that range in size from ∼45 kb to ∼140 kb. These plasmid-encoded toxins are often closely associated with mobile elements. A C. perfringens strain can carry up to three different toxin plasmids, with a single plasmid carrying up to three distinct toxin genes. Molecular Koch's postulate analyses have established the importance of several plasmid-encoded toxins when C. perfringens disease strains cause enteritis or enterotoxemias. Many toxin plasmids are closely related, suggesting a common evolutionary origin. In particular, most toxin plasmids and some antibiotic resistance plasmids of C. perfringens share an ∼35-kb region containing a Tn 916 -related conjugation locus named tcp (transfer of clostridial plasmids). This tcp locus can mediate highly efficient conjugative transfer of these toxin or resistance plasmids. For example, conjugative transfer of a toxin plasmid from an infecting strain to C. perfringens normal intestinal flora strains may help to amplify and prolong an infection. Therefore, the presence of toxin genes on conjugative plasmids, particularly in association with insertion sequences that may mobilize these toxin genes, likely provides C. perfringens with considerable virulence plasticity and adaptability when it causes diseases originating in the gastrointestinal tract.

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Section: Plasmid-encoded Toxinsmentioning

confidence: 99%

Section: Plasmid-encoded Toxinsmentioning

confidence: 99%

Toxin Plasmids of Clostridium perfringens

Adams

Bannam

et al. 2013

Microbiol Mol Biol Rev

231

282

View full text Add to dashboard Cite

show abstract

“…Using this threading technique, 3 of the 4 amino acid substitutions can be modeled; CPB is slightly larger than NetB (309 versus 293 amino acids, respectively) so the K40N substitution could not be modeled, as it is absent from NetB. This model predicts that the A300V switch occurs on one of 4 loops located near the bottom of the toxin, correlating with the predicted binding or rim domain of NetB (26,30). It appears likely that, based on the homology with NetB and our result, these 4 loops create the binding domain of CPB, although more work is needed to confirm this hypothesis.…”

Section: Discussionmentioning

confidence: 99%

“…To better understand the effects of the sequence variations on CPB trypsin sensitivity and cytotoxic activity, CPB was modeled in both the secreted and membrane-active forms by threading the CPB sequence onto the published (29,30) structures of C. perfringens delta and necrotic enteritis beta (NetB) toxins, respectively (Fig. 7).…”

Section: Discussionmentioning

confidence: 99%

“…To model the secreted form of CPB, the known structure of C. perfringens delta toxin was selected as the template (29). For modeling the active form of CPB, the known structure of the membrane-active form of C. perfringens necrotic enteritis beta toxin (NetB) was selected as the template (30). Once modeled, further analysis and labeling of the model were performed using PyMOL software.…”

Section: Methodsmentioning

confidence: 99%

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Identification and Characterization of Clostridium perfringens Beta Toxin Variants with Differing Trypsin Sensitivity and In Vitro Cytotoxicity Activity

2015

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b By producing toxins, Clostridium perfringens causes devastating diseases of both humans and animals. C. perfringens beta toxin (CPB) is the major virulence determinant for type C infections and is also implicated in type B infections, but little is known about the CPB structure-function relationship. Amino acid sequence comparisons of the CPBs made by 8 randomly selected isolates identified two natural variant toxins with four conserved amino acid changes, including a switch of E to K at position 168 (E168K) that introduces a potential trypsin cleavage site into the CPB protein of strain JGS1076. To investigate whether this potential trypsin cleavage site affects sensitivity to trypsin, a primary host defense against this toxin, the two CPB variants were assayed for their trypsin sensitivity. The results demonstrated a significant difference in trypsin sensitivity, which was linked to the E168K switch by using site-directed recombinant CPB (rCPB) mutants. The natural CPB variants also displayed significant differences in their cytotoxicity to human endothelial cells. This cytotoxicity difference was mainly attributable to increased host cell binding rather than the ability to oligomerize or form functional pores. Using rCPB site-directed mutants, differences in cytotoxicity and host cell binding were linked to an A300V amino acid substitution in the strain JGS1076 CPB variant that possessed more cytotoxic activity. Mapping of sequence variations on a CPB structure modeled using related toxins suggests that the E168K substitution is surface localized and so can interact with trypsin and that the A300V substitution is located in a putative binding domain of the CPB toxin. C lostridium perfringens is the etiological agent of numerous devastating diseases of both humans and animals (1). Illness caused by this Gram-positive, spore-forming bacterium is mediated by its extensive toxin arsenal, consisting of ϳ17 toxins. Four of these toxins are used to classify individual strains into one of five types, A to E, depending on which toxins are encoded. By definition, both type B and C strains must produce alpha toxin (CPA) and beta toxin (CPB); type B strains are distinguished from type C strains by also producing epsilon toxin (2, 3).Type B infection is typically confined to animals, including domestic livestock species, where it causes hemorrhagic enteritis and diarrhea, which may be accompanied by severe acute neurologic signs or sudden death (1, 4). Type C strains also cause animal diseases, typically in neonatal animals, which manifest as necrohemorrhagic enteritis and toxemia, resulting in rapid death of the animal (2, 4, 5). In addition to animal diseases, type C strains can infect people, causing enteritis necroticans (known regionally as Darmbrand or pig-bel) (6-9). These human infections, which are endemic in Southeast Asia, result in segmental necrotizing enteritis, which may lead to toxemia and are rapidly fatal without prompt medical intervention. Several predisposing factors for type C infection have been i...

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Necrotic Enteritis of Poultry

Cooper¹,

Songer²

2016

Clostridial Diseases of Animals

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Molecular Architecture and Functional Analysis of NetB, a Pore-forming Toxin from Clostridium perfringens

Cited by 99 publications

References 41 publications

Toxin Plasmids of Clostridium perfringens

Toxin Plasmids of Clostridium perfringens

Identification and Characterization of Clostridium perfringens Beta Toxin Variants with Differing Trypsin Sensitivity and In Vitro Cytotoxicity Activity

Necrotic Enteritis of Poultry

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