The esterolytic activity of epidermolytic toxins

Bailey, Christopher J.; Redpath, Maria B.

doi:10.1042/bj2840177

Cited by 28 publications

(31 citation statements)

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“…These structural similarities were most notable in the active site region known as the catalytic triad, which consists of three residues (His 72 , Asp 120 , and Ser 195 in ETA) that comprise the functional active site in a serine protease enzyme. Ser 195 and one mutant of Ser 195 (S195C, in which Ser 195 was mutated to Cys) have been studied in detail by several groups already (8,10,13). These findings contributed to the idea that ETA causes SSSS by acting directly or indirectly as an epidermal sitespecific serine protease.…”

mentioning

confidence: 81%

“…Furthermore, it has been shown that ETs have esterase activity (Ref. 13) and this study). However, protease activity has yet to be demonstrated.…”

Section: Discussionmentioning

confidence: 99%

“…Esterase assay N-t-Boc-L-glutamic acid ␣-phenyl ester (Sigma) was diluted to 500 mM in 1-4 dioxane and used as a substrate (13). Five microliters of 500 mM substrate was added to 3.0 g toxin suspended in 0.5 ml of 50 mM HEPES buffer (pH 7.4).…”

Section: Downloaded Frommentioning

confidence: 99%

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Mutational Analysis of the Superantigen Staphylococcal Exfoliative Toxin A (ETA)

Rago

Vath

Bohach

et al. 2000

The Journal of Immunology

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Exfoliative toxin A (ETA) is known to be a causative agent of staphylococcal scalded skin syndrome (SSSS). Although relatively little is known about exactly how the exfoliative toxins (ETs) cause SSSS, much has been discovered recently that may help elucidate the mechanism(s) by which ETA exhibits activities such as lymphocyte mitogenicity and epidermolytic activity. Here, we have shown that highly purified ETA does have T lymphocyte mitogenic activity in that wild-type ETA induced T cell proliferation whereas several single amino acid mutants lacked significant activity. Neither wild-type ETA nor any single amino acid mutants were proteolytic for a casein substrate, yet esterase activity was detected in wild-type ETA and several mutants, but eliminated in other mutants. A mutation in aa 164 (Asp to Ala) showed a 9-fold increase in esterase activity as well. Finally, we correlated esterase activity with epidermolytic activity. All mutants that lost esterase activity also lost epidermolytic activity. Conversely, mutants that retained esterase activity also retained exfoliative activity, implicating serine protease or serine protease-like activity in the causation of SSSS. Moreover, the mutants that displayed markedly reduced T cell superantigenic activity retained their epidermolytic activity (although some of these mutants required higher doses of toxin to cause disease), which suggests an ancillary role for this activity in SSSS causation.

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confidence: 81%

“…Furthermore, it has been shown that ETs have esterase activity (Ref. 13) and this study). However, protease activity has yet to be demonstrated.…”

Section: Discussionmentioning

confidence: 99%

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Mutational Analysis of the Superantigen Staphylococcal Exfoliative Toxin A (ETA)

Rago

Vath

Bohach

et al. 2000

The Journal of Immunology

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“…Protease activity has not been demonstrated for either toxin in vitro, but both ETA and ETB have intrinsic esterase activity, which is associated with serine proteases (3). Thus, it is likely that both toxins are proteases.…”

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confidence: 99%

RecombinantStaphylococcus aureusExfoliative Toxins Are Not Bacterial Superantigens

et al. 2000

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Staphylococcal scalded-skin syndrome is an exfoliative dermatitis characterized by the separation of the epidermis at the stratum granulosum. This disruption is mediated by one of two Staphylococcus aureus exotoxins, exfoliative toxins A and B (ETA and ETB). Both ETA and ETB have been reported to be bacterial superantigens. A controversy exists, however, as other data indicate that these exotoxins are not superantigens. Here we demonstrate that recombinant exfoliative toxins produced in Escherichia coli do not act as T-cell mitogens and thus are not bacterial superantigens. These data fit the clinical profile of the disease, which is not associated with the classic symptoms of a superantigen-mediated syndrome.Staphylococcal scalded-skin syndrome (SSSS) is an exfoliative dermatitis of infants and children that results from infection with exfoliative-toxin-producing Staphylococcus aureus (1,15). SSSS is characterized by the formation of large bullae without inflammatory cell infiltrate and separation of extended areas of the epidermis at the stratum granulosum leaving the keratinocytes intact. Two biologically and serologically distinct S. aureus exotoxins are responsible for the skin manifestations of SSSS in humans, exfoliative toxin A (ETA) and exfoliative toxin B (ETB) (25). ETA (26.9 kDa) is encoded on the bacterial chromosome and shares 40% amino acid identity with the plasmid-borne ETB (27.3 kDa) (2, 13, 19). Despite extensive studies, the exact mechanism responsible for the skin disruption is not known.X-ray crystallographic structures of ETA and ETB (5,20,23,24) suggest that the toxins are members of the trypsin-like serine protease family. Protease activity has not been demonstrated for either toxin in vitro, but both ETA and ETB have intrinsic esterase activity, which is associated with serine proteases (3). Thus, it is likely that both toxins are proteases. In addition to having possible protease activity, both ETA and ETB are reported to be bacterial superantigens (14,16,17,24). Bacterial superantigens are a family of proteins able to bind simultaneously to the major histocompatibility complex and to the T-cell receptor (TCR), resulting in stimulation of a large number of T cells expressing specific V␤ subsets of the TCR repertoire (14).Previously, Fleischer and Bailey reported that recombinant ETA expressed in a superantigen-free S. aureus background does not have mitogenic activity (7). They conclude that the activity seen by others is due to contamination of the toxin preparations with other superantigens. However, since this report, additional literature has addressed the superantigenic activity of ETA and ETB. Here we demonstrate that recombinant exfoliative toxins produced in an Escherichia coli background do not act as T-cell mitogens and thus are not bacterial superantigens.Isolation, expression, and purification of recombinant exfoliative toxins. DNA fragments encoding ETA and ETB were obtained by utilizing PCR and DNA from exfoliative-toxinproducing bacterial strains. Toxins were expressed a...

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“…It was reported that ExhA, ExhB, ExhC, ExhD, ETA and ETB show a certain similarity, exhibiting preservation of the catalytic tract of the active sites of the toxins (Ahrens & Andresen 2004). Evidence for a homologous relationship is that the catalytic triad His72, Asp120 and Ser195 of ETA align respectively with His65, Asp114 and Ser186 of ETB (Bailey & Redpath 1992). In ExhA-ExhC, His115, Asp164 and Ser239 are considered to be the catalytic triad, although the Asp164 in ExhD is replaced with a glutamate (Ahrens & Andresen 2004).…”

Section: Discussionmentioning

confidence: 99%

Critical roles of amino acids Ser231, His107 and Asp156 of Staphylococcus sciuri exfoliative toxin C (ExhC) in the induction of skin exfoliations in neonate mice

Zhang

et al. 2011

Biologia

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Staphylococcus sciuri is a rare pathogen in humans, but it can cause a wide array of human infections. Recently a strain of S. sciuri (HBXX06) carrying exfoliative toxin C (ExhC) was reported to cause fatal exudative epidermitis in piglets and might be considered as a potential zoonotic agent. However, little is known regarding the pathogenicity of this bacterium. In this study, we predicted the three-dimensional structure of S. sciuri HBXX06 ExhC and replaced Ser231 or His107 or Asp156 in the active site of ExhC by site-directed mutagenesis, and examined the effects of mutant ExhC on BHK-21 cells and newborn mice as models. Interestingly, we found that mutant ExhC lost its exfoliative effects on newborn mice but could still induce necrosis in cultured cells if any one of the three amino acid residues in the active site was replaced. These results suggest that Ser231, His107 and Asp156 of ExhC play a critical role in the induction of skin exfoliation in neonate mice, which may help to further understand the mechanisms underlying the actions of exfoliative toxins.

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The esterolytic activity of epidermolytic toxins

Cited by 28 publications

References 28 publications

Mutational Analysis of the Superantigen Staphylococcal Exfoliative Toxin A (ETA)

Mutational Analysis of the Superantigen Staphylococcal Exfoliative Toxin A (ETA)

RecombinantStaphylococcus aureusExfoliative Toxins Are Not Bacterial Superantigens

Critical roles of amino acids Ser231, His107 and Asp156 of Staphylococcus sciuri exfoliative toxin C (ExhC) in the induction of skin exfoliations in neonate mice

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