Shiga toxin
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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.Cite error: Closing </ref> missing for <ref> tag
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.
