Enteropathogenic E. coli Infection Mechanism Part 2: The bacterium injects webpart2.mov Print a PDF of the Lesson Narrative |
The tethered bacterium now uses a specialized injector system to deliver some of its own proteins into the cell that it is invading. The injector systems that bacteria use are fascinating and are composed of several different proteins. In this case a Type III injector system is used, which is specialized for pumping things into other cells. The bacterium uses the injector system, much like a syringe, to introduce several bacterial proteins into the intestinal cell that force it to cooperate in its own infection. A needlelike tube (purple) called EspA projects from the bacterium to the intestinal cell surface. Now two proteins (green) named EspB and EspD travel through the tube to form an opening in the intestinal membrane through which additional bacterial proteins can move into the cell. With the tube and pore complete, the bacterium now injects a protein called Tir (red) into the cell. The Tir proteins insert themselves into the intestinal cell membrane. A portion of the Tir protein projects beyond the cell surface and binds to a protein on the bacterial cell surface called intimin (blue cups). Now the membranes of the intestinal cell and the bacterium are locked together, and the intestinal cell is in trouble. The Tir proteins become phosphorylated by intestinal cell proteins (blue balls). The stage is set for the next step, pedestal formation. |