The barrel is oriented in the membrane such that the N-terminal portion of the protein, termed the passenger domain, is presented on the cell surface.

The name autotransporter derives from an initial understanding that the protein was self-sufficient in transporting the passenger domain through the outermembrane.

[2] Secretion of polypeptide chains through the outer membrane of Gram-negative bacteria can occur via a number of different pathways.

Passenger domains structurally characterized to date have been shown to be dominated by a protein fold known as a beta helix, typified by pertactin.

The folding of this domain is thought to be intrinsically linked to its method of outer membrane translocation.