Bacterial exotoxin B (IPR003896)

Short name: Bacterial_exotoxin_B

Overlapping homologous superfamilies


Family relationships



A large group of bacterial exotoxins are referred to as "A/B toxins", essentially because they are formed from two subunits [PMID: 8225592]. The "A" subunit possesses enzyme activity, and is transferred to the host cell following a conformational change in the membrane-bound transport "B" subunit. Clostridial species are one of the major causes of food poisoning/gastro-intestinal illnesses. They are Gram-positive, spore-forming rods that occur naturally in the soil [PMID: 8225592]. Among the toxins produced by certain Clostridium spp. are the binary exotoxins. These proteins consist of two independent polypeptides, which correspond to the A/B subunit moieties. The enzyme component (A) enters the cell through endosomes produced by the oligomeric binding/translocation protein (B), and prevents actin polymerisation through ADP-ribosylation of monomeric G-actin [PMID: 8225592, PMID: 9659689, PMID: 10802189].

Members of the "B" binary toxin family also include the Bacillus anthracis protective antigen (PA) protein [PMID: 8225592], most likely due to a common evolutionary ancestor. B. anthracis, a large Gram-positive spore-forming rod, is the causative agent of anthrax. Its two virulence factors are the poly-D-glutamate polypeptide capsule, and the actual anthrax exotoxin [PMID: 1910002]. The toxin comprises three factors: the protective antigen (PA); the oedema factor (EF); and the lethal factor (LF). Each is a thermolabile protein of ~80kDa. PA forms the "B" part of the exotoxin and allows passage of the "A" moiety (consisting of EF and LF) into target cells. PA protein forms the central part of the complete anthrax toxin, and translocates the B moiety into host cells after assembling as a heptamer in the membrane [PMID: 1910002, PMID: 3148491].

GO terms

Biological Process

GO:0009405 pathogenesis

Molecular Function

No terms assigned in this category.

Cellular Component

GO:0005576 extracellular region

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.