FIG. 9.

Model for Ysc-dependent and independent secretion of LcrV. LcrV, YopB, YopD, and possibly other proteins (X) are secreted by contact-activated Ysc secretion channels and assemble into an apparatus that mediates targeting of secreted Yops across the plasma membrane and into the cytoplasm of eukaryotic cells. LcrV shed from these structures diffuses into the surrounding medium. The LcrV-transporting contact-activated translocator (VCAT) can also secrete LcrV from Yersinia. Upon contact with the plasma membrane, LcrV not involved in secretion or targeting of Yops is secreted across the inner membrane (IM), periplasm (PP), and outer membrane (OM) of Y. pestis through the VCAT mechanism composed of non-pCD1-encoded proteins. LcrV secreted in this manner is delivered directly to associated eukaryotic cells.