Editing Secretion (section)

====Function====
The Type IV secretion system (T4SS) is the general mechanism by which bacterial cells secrete or take up macromolecules. Their precise mechanism remains unknown. T4SS is encoded on [[Gram negative bacteria|Gram-negative]] conjugative elements in [[bacteria]]. T4SS are cell envelope-spanning complexes, or, in other words, 11–13 core proteins that form a channel through which DNA and proteins can travel from the cytoplasm of the donor cell to the cytoplasm of the recipient cell. T4SS also secrete [[virulence]] factor proteins directly into host cells as well as taking up DNA from the medium during natural [[Transformation (bacteria)|transformation]].<ref name="pmid12855161">{{cite journal | vauthors = Lawley TD, Klimke WA, Gubbins MJ, Frost LS | title = F factor conjugation is a true type IV secretion system | journal = FEMS Microbiology Letters | volume = 224 | issue = 1 | pages = 1–15 | date = July 2003 | pmid = 12855161 | doi = 10.1016/S0378-1097(03)00430-0 | doi-access = free }}</ref>