The Type IV secretion system (T4SS). A large protein complex through which protein or protein-DNA complexes can be translocated. This animation shows (in part) the T4SS of Helicobacter pylori. A Gram-negative bacterium which is linked to the development of duodenal ulcers and stomach cancer. The T4SS plays an important role in this process. The red protein which is secreted in this animation is CagA. After its secretion, CagA can be inserted into the cell membrane of gastric epithelial cells. In