diphteriatoksiinia

Diphtheria toxin is a protein produced by the bacterium Corynebacterium diphtheriae, which causes the disease diphtheria. The toxin is a key virulence factor that enables the bacterium to infect its host. It is an exotoxin, meaning it is secreted by the bacteria into the surrounding environment.

The toxin is encoded by a gene, tox, which is carried by a bacteriophage that infects the bacterium. Strains of Corynebacterium diphtheriae that do not carry the tox gene are non-pathogenic. The toxin is a single polypeptide chain that is cleaved into two fragments, A and B, upon entering the host cell. Fragment A is the active component that inhibits protein synthesis, while fragment B binds to specific receptors on the host cell surface and facilitates the entry of fragment A.

The mechanism of action of diphtheria toxin involves the irreversible inactivation of elongation factor 2 (EF-2), a crucial protein required for the translocation of transfer RNA during protein synthesis. By blocking EF-2, the toxin halts all protein production in the cell, leading to cell death. This cellular damage is particularly severe in tissues with high protein synthesis rates, such as the heart and nervous system, which are often affected in severe diphtheria cases.

Diphtheria toxin is highly potent, and even very small amounts can cause significant illness. The severity of diphtheria symptoms is directly related to the amount of toxin produced and released into the body. Immunity to diphtheria toxin is achieved through vaccination, which stimulates the production of neutralizing antibodies that bind to and inactivate the toxin. This antitoxin immunity is the basis of successful diphtheria prevention.