Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 produces Shiga-like toxins Stx(s) or verotoxins. The Stxs consists of one StxA subunit and five StxB subunits toxins. The StxB is responsible for toxin attachment to the host cell. It's worth noting that the B-subunits still form pentamers even in the absence of the A-subunit. They are functionally equivalent to the holotoxin in their binding to cell surface glycolipids. The B subunit is important in the interaction between the bacteria and Gb3 receptors in the microvasculature of the gastrointestinal tract and central nervous system, resulting in subsequent endothelial cell injury and microvascular thrombosis in the affected organs. Binding of the subunit B to Gb3 causes induction of narrow tubular membrane invaginations. It drives the formation of inward membrane tubules for the bacterial uptake into the cell. These tubules are essential for uptake into the host cell.
EHEC is a causative agent of many severe human illnesses such as bloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. The mortality rate in children and elder people may reach over 50%. The toxin is effective against small blood vessels, such as found in the digestive tract, the kidney, and lungs, but not against large vessels such as the arteries or major veins. A specific target for the toxin appears to the vascular endothelium of the glomerulus.
For Research Use Only. NOT FOR CLINICAL USE.
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