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Shiga bacillusShigella dysenteriae.
The toxin acts on the endothelial cells lining the blood vessels. The B subunits of the toxin bind to a component of the cell membrane known as Gb3 and enter the cell. When the protein is inside the cell, the A subunit interacts with the ribosomes to stop protein synthesis. Like the ricin toxin, the A subunit of Shiga toxin is an N-glycosidase that modifies the RNA component of the ribosome to stop protein synthesis, leading to the death of the cell. The breakdown of the endothelial cell lining leads to hemorrhage.
The first sign of shiga toxin activity is usually bloody diarrhea. This is because Shiga toxin is usually taken in with contaminated food or water.