FIGURE 6.

Schematic of ExoU membrane association and conformational changes. The ExoU four-helix bundle (cylinders) is depicted as dissociating and being displaced from the catalytic domain (rectangles) upon adoption of the holo state (upper right), accompanied by conformational changes in the bridging domain (oval) and catalytic domain that expose the catalytic site (star) to the membrane surface (located at the top of the figure). The binding of ubiquitin (octagon) and membrane association in the absence of ubiquitin (upper left) likely result in conformational changes relative to the apo state (lower left) that remain to be elucidated, and the location of the ubiquitin-binding site has not been fully identified.