Type IV secretion system

[2] Type IV secretion systems are used for conjugation, DNA exchange with the extracellular space, and for delivering proteins to target cells.

Notable instances of the type IV secretion system include the plasmid insertion into plants of Agrobacterium tumefaciens, the toxin delivery methods of Bordetella pertussis (whooping cough) and Legionella pneumophila (Legionnaires' disease), the translocation of effector proteins into host cells by bacteria from the Brucella genus (Brucellosis), and the F sex pilus.

Primarily, type IV secretion systems are grouped based on structural and genetic similarity and are only distantly related to each other.

[4] Conjugative as well as DNA release and uptake systems play an important role in horizontal gene transfer, which allows prokaryotes to adapt to their environment, such as, developing antibiotic resistance.

The effector systems are used as a toxin delivery method by many human pathogens such as, Helicobacter pylori (stomach ulcers), whooping cough, and Legionnaires' disease.

[1] The Type IV secretion system’s components can be separated into 3 groups: the translocation channel scaffold, the ATPases, and the pilus.

The core complex of the scaffold is composed of 14 copies of VirB7, VirB9, and VirB10 which form a cylindrical channel that spans both membranes and connects the cytoplasm to the extracellular space.

[2] Due to the wide variety of type IV secretion systems in both origin and function, it is difficult to state much mechanistically about the group as a whole.