Lom is found in the bacterial outer membrane, and is homologous to virulence proteins of two other enterobacterial genera.

The core of the barrel consists of an extended hydrogen bonding network of highly conserved residues.

It is suggested that this type of binding promotes cell adhesion and invasion and helps defend against the complement system.

Although OmpX has the same beta-sheet topology as the structurally related outer membrane protein A (OmpA) InterPro: IPR000498, their barrels differ with respect to the shear numbers and internal hydrogen-bonding networks.

OspA from Borrelia burgdorferi is an unusual outer surface protein, it has two globular domains which are connected with a single-layer β-sheet.