Shiga toxin
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==Introduction== | ==Introduction== | ||
| - | '''Shiga Toxins''' are a family of AB5 toxins which cause dysentery in humans. They are primarily secreted by Shiga toxin-encoding Escherichia coli (STEC), notably by the 0157:H7 strain. The stx gene is not endogenous to these strains, but introduced by environmental prophages of the lambda bacteriophage family and incorporated into the E. Coli genome | + | '''Shiga Toxins''' are a family of AB5 toxins which cause dysentery in humans. They are primarily secreted by Shiga toxin-encoding Escherichia coli (STEC), notably by the 0157:H7 strain.<ref name=Wagner> The stx gene is not endogenous to these strains, but is introduced by environmental prophages of the lambda bacteriophage family and incorporated into the E. Coli genome.<ref name=Wagner>PMID: 12010491</ref> |
| + | ==Structure== | ||
| + | Shiga Toxin consists consists of an [http://en.wikipedia.org/wiki/AB5_toxin AB5] hexamer, by X-ray crystallography. The five B subunits form a pentameric ring, encircling a helix at the carboxy terminus of the A subunit. The A subunit interacts with the B pentamer via this C-terminal helix and a four-stranded mixed beta-sheet. The fold of the rest of the A subunit is similar to that of the A chain of the plant toxin ricin; both are N-glycosidases. However, the active site in the bacterial holotoxin is blocked by a segment of polypeptide chain. These residues of the A subunit would be released as part of the activation mechanism of the toxin. | ||
| - | == | + | ==References== |
| - | + | {{Reflist}} | |
Revision as of 01:11, 14 October 2011
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Introduction
Shiga Toxins are a family of AB5 toxins which cause dysentery in humans. They are primarily secreted by Shiga toxin-encoding Escherichia coli (STEC), notably by the 0157:H7 strain.[1]
Structure
Shiga Toxin consists consists of an AB5 hexamer, by X-ray crystallography. The five B subunits form a pentameric ring, encircling a helix at the carboxy terminus of the A subunit. The A subunit interacts with the B pentamer via this C-terminal helix and a four-stranded mixed beta-sheet. The fold of the rest of the A subunit is similar to that of the A chain of the plant toxin ricin; both are N-glycosidases. However, the active site in the bacterial holotoxin is blocked by a segment of polypeptide chain. These residues of the A subunit would be released as part of the activation mechanism of the toxin.
References
- ↑ The stx gene is not endogenous to these strains, but is introduced by environmental prophages of the lambda bacteriophage family and incorporated into the E. Coli genome.<ref>PMID: 12010491</li></ol></ref>
