Shiga toxin: Difference between revisions

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{{STRUCTURE_2xsc| PDB=2xsc | SIZE=400| SCENE= |right|CAPTION=E. coli Shiga-like toxin 1 subunit B pentamer complex with Zn+2 (grey) ions [[2xsc]] }}
<StructureSection load='2xsc' size='450' side='right' scene='' caption=''>


==Introduction==
==Introduction==
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Shiga Toxin acts as an N-glycosidase, removing an adenine from the 28S ribosomal rRNA of a target cell which leads to inhibition of protein elongation and ultimately cellular apoptosis.<ref name=Di>PMID: 21184769</ref>  The B subunit is necessary for binding to globo series glycolipid globotriaosylceramide (Gb<sub>3</sub>), a eukaryotic membrane receptor, where it is then endocytosed and proteolytically cleaved into an active A subunit and a B subunit.<ref name=Lenz>PMID: 2170899</ref>  The B subunit is not active in the depurination of of 28S rRNA, but is essential for GB<sub>3</sub> binding and therefore essential for toxicity.  Once in the cytosol the A subunit is free to interact with and inactivate 28S rRNA.  On the A subunit <scene name='Shiga_toxin_1/Active_site_zoomed_in/1'>Tyr77, Tyr114, Glu167, Arg170, and Trp203</scene> are all essential in glycosidic activity.<ref name=Di>PMID: 21184769</ref>  This mechanism (B subunit binding to globotriaosylceramide and A subunit depurinating 28S rRNA) is conserved amongst the Stx family as well as the ricin toxin.
Shiga Toxin acts as an N-glycosidase, removing an adenine from the 28S ribosomal rRNA of a target cell which leads to inhibition of protein elongation and ultimately cellular apoptosis.<ref name=Di>PMID: 21184769</ref>  The B subunit is necessary for binding to globo series glycolipid globotriaosylceramide (Gb<sub>3</sub>), a eukaryotic membrane receptor, where it is then endocytosed and proteolytically cleaved into an active A subunit and a B subunit.<ref name=Lenz>PMID: 2170899</ref>  The B subunit is not active in the depurination of of 28S rRNA, but is essential for GB<sub>3</sub> binding and therefore essential for toxicity.  Once in the cytosol the A subunit is free to interact with and inactivate 28S rRNA.  On the A subunit <scene name='Shiga_toxin_1/Active_site_zoomed_in/1'>Tyr77, Tyr114, Glu167, Arg170, and Trp203</scene> are all essential in glycosidic activity.<ref name=Di>PMID: 21184769</ref>  This mechanism (B subunit binding to globotriaosylceramide and A subunit depurinating 28S rRNA) is conserved amongst the Stx family as well as the ricin toxin.


{{STRUCTURE_2ga4|  PDB=2ga4  | SIZE=400| SCENE= |right|CAPTION=Shiga-like toxin II complex with adenine, sulfopropyl-pyridinium, ethylene glycol, formic acid and sodium ions [[2ga4]] }}
</StructureSection>
__NOTOC__
 


==3D structures of shiga toxin==
==3D structures of shiga toxin==
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