Shiga toxin: Difference between revisions
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==Structure== | ==Structure== | ||
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 | Shiga Toxin consists consists of an [http://en.wikipedia.org/wiki/AB5_toxin AB5] hexamer.<ref name=Fraser>PMID: 7656009</ref> The <scene name='Shiga_toxin/B_subunits/1'>5 subunit B pentamer</scene> interacts with the <scene name='Shiga_toxin/A_subunits/1'>two separate A subunits</scene> via a C-terminal helix and 4 stranded beta-sheet.<ref name=Fraser>PMID: 7656009</ref>. 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>PMID: 7656009</ref> | ||
==Function== | ==Function== | ||
Revision as of 06:37, 14 October 2011
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IntroductionIntroduction
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] 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.[1]
StructureStructure
Shiga Toxin consists consists of an AB5 hexamer.[2] The interacts with the via a C-terminal helix and 4 stranded beta-sheet.[2]. 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.[2]
FunctionFunction
Shiga Toxin acts as an N-glycosidase, removing an adenine from the 60S ribosomal rRNA of a target cell leading to reduced protein synthesis.[3] 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 are all essential in glycosidic activity.[3]
ReferencesReferences
- ↑ 1.0 1.1 Wagner PL, Livny J, Neely MN, Acheson DW, Friedman DI, Waldor MK. Bacteriophage control of Shiga toxin 1 production and release by Escherichia coli. Mol Microbiol. 2002 May;44(4):957-70. PMID:12010491
- ↑ 2.0 2.1 2.2 Fraser ME, Chernaia MM, Kozlov YV, James MN. Crystal structure of the holotoxin from Shigella dysenteriae at 2.5 A resolution. Nat Struct Biol. 1994 Jan;1(1):59-64. PMID:7656009
- ↑ 3.0 3.1 Di R, Kyu E, Shete V, Saidasan H, Kahn PC, Tumer NE. Identification of amino acids critical for the cytotoxicity of Shiga toxin 1 and 2 in Saccharomyces cerevisiae. Toxicon. 2011 Mar 15;57(4):525-39. Epub 2010 Dec 22. PMID:21184769 doi:10.1016/j.toxicon.2010.12.006