Fig. 9. Model for AT secretion. The AT proteins assemble as a ring-shaped oligomeric complex in the bacterial OM. A minimum of six monomers assemble in this complex. The N-terminal passenger domains (P) are depicted as ovals and the C-terminal transporter domain as cylinders anchored in the OM lipid bilayer. The N-domains are translocated from the periplasm (left) to the external medium (right) by passing through the central hydrophilic pore formed by an AT oligomeric complex.