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146  structures 133  species 0  interactions 261  sequences 2  architectures

Family: SLT_beta (PF02258)

Summary: Shiga-like toxin beta subunit

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This is the Wikipedia entry entitled "Shiga-like toxin". More...

Shiga-like toxin Edit Wikipedia article

Shiga-like toxin beta subunit
2XSC.pdb.png
Identifiers
Symbol SLT_beta
Pfam PF02258
InterPro IPR003189
SCOP 2bos
SUPERFAMILY 2bos
TCDB 1.C.54

Shiga-like toxin, also known as verotoxin,[1][2] is a toxin generated by some strains of Escherichia coli (but see below).[3] It is named for its similarity to the AB5-type Shiga toxin produced by the bacteria Shigella dysenteriae, [ see Vero cell ].

There are two types, known as SLT1 and SLT2.[4]

History[edit]

Transmission[edit]

As with Shiga toxin, the toxin requires highly specific receptors on the cells' surface in order to attach and enter the cell; species such as cattle, swine, and deer which do not carry these receptors may harbor toxigenic bacteria without any ill effect, shedding them in their feces, from where they may be spread to humans.

Clinical significance[edit]

Shiga-toxin is associated with Hemolytic-uremic syndrome.

Structure and mechanism[edit]

SLT2 from Escherichia coli O157:H7. The A subunit is shown in red (top), and the B subunits, forming a pentamer, in different shades of blue (bottom). From PDB 1R4P.

Structure[edit]

The toxin is a multisubunit protein made up one molecule of A subunit (32,000 molecular weight) responsible for the toxic action of the protein, and five molecules of the B subunit (7,700 molecular weight) responsible for binding to a specific cell type.

Mechanism of action[edit]

The toxin acts on the lining of the blood vessels, the vascular endothelium. The B subunits of the toxin bind to a component of the cell membrane known as glycolipid globotriaosylceramide (Gb3).[5] Binding of the subunit B to Gb3 causes induction of narrow tubular membrane invaginations, which drives formation of inward membrane tubules for the bacterial uptake into the cell. These tubules are essential for uptake into the host cell.[6] When the protein is inside the cell, the A subunit interacts with the ribosomes to inactivate them. The A subunit of Shiga toxin is an N-glycosidase that modifies the RNA component of the ribosome to inactivate it and so bring a halt to protein synthesis leading to the death of the cell. The vascular endothelium has to continually renew itself, so this killing of cells leads to a breakdown of the lining and to hemorrhage. The first response is commonly a bloody diarrhea. This is because Shiga toxin is usually taken in with contaminated food or water.

The toxin is effective against small blood vessels, such as found in the digestive tract, the kidney, and lungs, but not against large vessels such as the arteries or major veins. A specific target for the toxin appears to the vascular endothelium of the glomerulus. This is the filtering structure that is a key to the function of the kidney. Destroying these structures leads to kidney failure and the development of the often deadly and frequently debilitating hemolytic uremic syndrome. Food poisoning with Shiga toxin often also has effects on the lungs and the nervous system.

Source of toxin gene[edit]

It has been suggested by some researchers that the gene coding for Shiga-like toxin comes from a toxin-converting lambdoid prophage, such as H-19B or 933W, inserted into the bacteria's chromosome via transduction.[7]

See also[edit]

References[edit]

  1. ^ Beutin L, Geier D, Steinrück H, Zimmermann S, Scheutz F (September 1993). "Prevalence and some properties of verotoxin (Shiga-like toxin)-producing Escherichia coli in seven different species of healthy domestic animals". Journal of clinical microbiology 31 (9): 2483–8. PMC 265781. PMID 8408571. 
  2. ^ Bitzan M, Richardson S, Huang C, Boyd B, Petric M, Karmali MA (August 1994). "Evidence that verotoxins (Shiga-like toxins) from Escherichia coli bind to P blood group antigens of human erythrocytes in vitro". Infection and immunity 62 (8): 3337–47. PMC 302964. PMID 8039905. 
  3. ^ Giraldi R, Guth BE, Trabulsi LR (June 1990). "Production of Shiga-like toxin among Escherichia coli strains and other bacteria isolated from diarrhea in São Paulo, Brazil". Journal of clinical microbiology 28 (6): 1460–2. PMC 267957. PMID 2199511. 
  4. ^ Zhu Q, Li L, Guo Z, Yang R (June 2002). "Identification of Shiga-like toxin Escherichia coli isolated from children with diarrhea by polymerase chain reaction". Chin. Med. J. 115 (6): 815–8. PMID 12123543. 
  5. ^ Kaper, JB; Nataro, JP, Mobley, HL (Feb 2004). "Pathogenic Escherichia coli.". Nature reviews. Microbiology 2 (2): 123–40 [129]. doi:10.1038/nrmicro818. PMID 15040260. 
  6. ^ Römer W, Berland L, Chambon V, et al. (November 2007). "Shiga toxin induces tubular membrane invaginations for its uptake into cells". Nature 450 (7170): 670–5. doi:10.1038/nature05996. PMID 18046403. 
  7. ^ Satoshi MIZUTANI, Naoki NAKAZONO, and Yoshinobu SUGINO (1999). "The So-called Chromosomal Verotoxin Genes are Actually Carried by Defective Prophages". Dna Research 6 (2): 141–143. doi:10.1093/dnares/6.2.141. PMID 10382973. 
  8. ^ Stein PE, Boodhoo A, Tyrrell GJ, Brunton JL, Read RJ (February 1992). "Crystal structure of the cell-binding B oligomer of verotoxin-1 from E. coli". Nature 355 (6362): 748–50. doi:10.1038/355748a0. PMID 1741063. 

External links[edit]

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

Shiga-like toxin beta subunit Provide feedback

This family represents the B subunit of shiga-like toxin (SLT or verotoxin) produced by some strains of E.coli associated with hemorrhagic colitis and hemolytic uremic syndrome. SLT's are composed of one enzymatic A subunit and five cell binding B subunits.

Literature references

  1. Ling H, Pannu NS, Boodhoo A, Armstrong GD, Clark CG, Brunton JL, Read RJ; , Structure Fold Des 2000;8:253-264.: A mutant Shiga-like toxin IIe bound to its receptor Gb(3): structure of a group II Shiga-like toxin with altered binding specificity. PUBMED:10745005 EPMC:10745005


External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR003189

This family represents the B subunit of shiga-like toxin (SLT or verotoxin) produced by some strains of Escherichia coli associated with hemorrhagic colitis and hemolytic uremic syndrome. SLT s are composed of one enzymatic A subunit and five cell binding B subunits.

Gene Ontology

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Domain organisation

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RP55
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RP75
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  Seed
(2)
Full
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Representative proteomes NCBI
(142)
Meta
(0)
RP15
(0)
RP35
(0)
RP55
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RP75
(1)
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Curation and family details

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Seed source: Pfam-B_3684 (release 5.2)
Previous IDs: none
Type: Domain
Author: Bateman A, Mian N
Number in seed: 2
Number in full: 261
Average length of the domain: 67.60 aa
Average identity of full alignment: 81 %
Average coverage of the sequence by the domain: 78.02 %

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HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 21.1 21.1
Trusted cut-off 21.2 21.5
Noise cut-off 21.0 20.9
Model length: 70
Family (HMM) version: 11
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Structures

For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the SLT_beta domain has been found. There are 146 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.

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