Shiga toxin
From Proteopedia
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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.<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> | + | '''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>PMID: 12010491</ref> 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== | ==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 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> | + | 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>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== | ||
| - | 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> | + | |
| + | 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 <scene name='Shiga_toxin/Active_site/1'>Tyr77, Tyr114, Glu167, Arg170, and Trp203</scene> are all essential in glycosidic activity.<ref name=Di>PMID: 21184769</ref> | ||
==References== | ==References== | ||
{{Reflist}} | {{Reflist}} | ||
Revision as of 03:22, 14 October 2011
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Contents |
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] 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]
Structure
Shiga Toxin consists consists of an AB5 hexamer.[2] The 5 subunit B pentamer interacts with a single A subunit 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]
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.[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]
References
- ↑ 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
