Shiga toxin
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Shiga toxins are a family of related toxins with two major groups, Stx1 and Stx2, whose genes are considered to be part of the genome of lambdoid prophages. Shiga toxins act to inhibit protein synthesis within target cells.
Shiga toxins are extremely similar to ricin. After entering a cell, the protein functions as an N-glycosidase, cleaving several nucleobases from the RNA that comprises the ribosome, thereby halting protein synthesis.
The most common sources for Shiga toxin are the bacteria Shigella dysenteriae and the O157:H7 strain of Escherichia coli. The Shiga toxin found in Escherichia coli is also known as Shiga-like toxin although it is equivalent to the Shiga toxin produced by Shigella dysenteriae.