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Cholera toxin mechanism. Cholera toxin (also known as choleragen and sometimes abbreviated to CTX, Ctx or CT) is an AB5 multimeric protein complex secreted by the bacterium Vibrio cholerae. [1] [2] CTX is responsible for the massive, watery diarrhea characteristic of cholera infection. [3] It is a member of the heat-labile enterotoxin family.
These toxins consist of an AB5 multimer structure, in which a pentamer of B chains has a membrane-binding function and an A chain is needed for enzymatic activity. [3] The B subunits are arranged as a doughnut-shaped pentamer, each subunit participating in ~30 hydrogen bonds and 6 salt bridges with its two neighbours.
Sambhu Nath De isolated the cholera toxin and demonstrated the toxin as the cause of cholera in 1959. The bacterium has a flagellum (a tail like structure) at one pole and several pili throughout its cell surface. It undergoes respiratory and fermentative metabolism.
Ribbon diagram of cholera toxin. From Ribbon diagram of pertussis toxin. S1 is the A subunit, and S2-S5 make up the B subunit. [3] Ribbon diagram of shiga toxin (Stx) from Shigella dysenteriae, showing the characteristic AB5 structure.
The cholera toxin (CTX or CT) is an oligomeric complex made up of six protein subunits: a single copy of the A subunit (part A), and five copies of the B subunit (part B), connected by a disulfide bond. The five B subunits form a five-membered ring that binds to GM1 gangliosides on the surface of the intestinal epithelium cells.
This allows the body to detect the harmful toxin if it is encountered later, and to eliminate it before it can cause harm to the host. Toxins of this type include cholera toxin, pertussis toxin, Shiga toxin and heat-labile enterotoxin from E. coli.
The AB toxins are two-component protein complexes secreted by a number of pathogenic bacteria, though there is a pore-forming AB toxin found in the eggs of a snail. [1] They can be classified as Type III toxins because they interfere with internal cell function. [ 2 ]
structure summary: An enterotoxin is a ... These toxins share the ability to bind to the major histocompatibility complex proteins of their hosts. ... (Cholera toxin ...