AB5 toxin

The AB5 toxins are six-component protein complexes secreted by certain pathogenic bacteria known to cause human diseases such as cholera, dysentery, and hemolytic-uremic syndrome. One component is known as the A subunit, and the remaining five components make up the B subunit. All of these toxins share a similar structure and mechanism for entering targeted host cells. The B subunit is responsible for binding to receptors to open up a pathway for the A subunit to enter the cell. The A subunit is then able to use its catalytic machinery to take over the host cell's regular functions.

There are four main families of the AB5 toxin. These families are characterized by the sequence of their A subunit, as well as their catalytic ability.

This family is also known as Ct or Ctx, and includes the heat-labile enterotoxin family, known as LT. Cholera toxin’s discovery is credited by many to Dr. Sambhu Nath De. He conducted his research in Calcutta (now Kolkata) making his discovery in 1959, although it was first purified by Robert Koch in 1883. Cholera toxin is an infectious toxin composed of a protein complex that is secreted by the bacterium Vibrio cholerae. Some symptoms of this toxin include chronic and widespread watery diarrhea and dehydration that, in some cases, leads to death.

This family is also known as Ptx and contains the toxin responsible for whooping cough. Pertussis toxin is secreted by the gram-negative bacterium, Bordetella pertussis. Whooping cough is very contagious and cases are slowly increasing in the United States despite vaccination. Symptoms include paroxysmal cough with whooping and even vomiting. The bacterium Bordetella pertussis was first identified as the cause of whooping cough and isolated by Jules Bordet and Octave Gengou in France in 1900.

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