Food Poison: Cellular Toxicity Caused By Nhe Was First Revealed in a Doctoral Thesis
Recently a doctoral research revealed a protein structure of how Bacillus cereus causes toxin. The author is Danh Phung, he found the crystalline structure of NheA. Phung's study is the first to show that the Nhe proteins form structures resembling pores.
We know that food poisoning caused by Bacillus cereus can lead to diarrhea. The research revealed that this is probably caused by a 3-component toxin by this bacteria strain and then perforates and kills cells.
The new finding leads to a better understanding of the mechanisms behind multi-component, pore-forming toxins. These findings are important for improving food safety.
Pore-forming toxins account 1/3 of all bacterial toxins. From the name we can speculate that these toxins kill cells by making holes in the cell walls, so causing leakages and swelling which in turn leads to the disintegration of the cells. The most common pore-forming toxins consist of one protein and in some special cases, of two proteins.
Toxins which consist of three proteins (3-component) are extremely rare. The bacterium Bacillus cereus produces two such 3-component toxins. One of them is non-hemolytic enterotoxin, also known as Nhe. It is believed that this toxin is the major food poisoning toxin produced by B. cereus. It is found in all B. cereus strains that cause food poisoning and in nearly all other B. cereus strains. The three proteins in the Nhe toxin are called NheA, NheB and NheC.
NheA, a protein, the least studied of this toxin complex, but its presence is essential in order to achieve full cellular toxicity and pore formation.
In addition to this, Phung showed that NheB, which is believed to be the most important protein in this toxin complex, forms pore-like structures of itself and produces large amounts of molecules by means of an artificial cell membrane, for example a lipid. These findings indicate that the NheB protein undergoes structural changes before the pore-forming process, which involves the other Nhe-proteins, begins.
Danh Phung carried out her doctoral research at the Norwegian School of Veterinary Science in collaboration with the Sir Hans Krebs Institute at the University of Sheffield in the UK.
Tags: NheA, Cell Toxin, Food Safety, Bacillus cereus, Cell Strains