Shiga toxins are a family of related bacterial toxins first discovered by Kiyoshi Shiga while researching the origins of dysentary. Two major groups of this toxin are found in the Shigella dysenteriae and the shigatoxigenic serotypes of Escherichia coli bacteria, Stx1 and Stx2.
As the name suggests, this little bugger causes pretty bad dysentery in humans. Shiga-like Toxin is made of 6 primary chains, 5 smaller identical subunits that form a pentamer ring and then the Alpha unit. The two red domains on top are the functionally toxic portions of the protein.
The pentamer is the portion of the compound that binds to surface receptors anchoring the Alpha unit toxin to the membrane. Upon binding, the Alpha unit forces itself into the cytosol. Following this, a predict bile sequence of events occurs that directly inactivates ribosomes halting protein synthesis.