Fig. 6.

Model for the function of VirB4 during the type IV secretion process. VirB4 is shaded in gray as two domains linked by a hinge (solid line). VirB11 and VirD4 are black and stippled, respectively. For simplicity, only two subunits of VirB4, VirD4, and VirB11 are shown, and the rest of the T4SS is drawn as a half cylinder. VirD2 is shown as a white square attached to the T-strand (wave ladder-like line). Arrows indicate subunit exchange between VirB4 and VirD4. See text for details. OM, outer membrane; IM, inner membrane.