Shiga toxin: Difference between revisions

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Max Evoy-Mount, Michal Harel, Alexander Berchansky

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 ==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.
+Shiga Toxin consists consists of an [http://en.wikipedia.org/wiki/AB5_toxin AB5] hexamer.<ref name=Fraser>PMID: 7656009</ref> The 5 subunit B pentamer interacts with a single A subunit via a C-terminal helix and 4 stranded beta-sheet.<ref name=Fraser> The glycosidase active site is located on the A subunit, but is blocked by the B subunit until they are cleaved and an active A subunit is released into the target cell.<ref name=Fraser>
+==Function==
+Shiga Toxin acts as an N-glycosidase, removing an adenine from the 60S ribosomal rRNA of a target cell leading to reduced protein synthesis.<ref name=Di>PMID: 21184769</ref>  The B subunit is necessary for binding to eukaryotic cell surface, where it is then endocytosed and proteolytically cleaved into two active A subunits and a B subunit.  On the A subunit Tyr77, Tyr114, Glu167, Arg170, and Trp203 are all essential in glycosidic activity.<ref name=Di>
 ==References==
 {{Reflist}}