Members of this family are Major Outer Membrane Proteins of Porphyromonas gingivalis. Porphyromonas gingivalis possesses various abilities to evade and disrupt host immune responses, by which it acts as an important periodontal pathogen. P. gingivalis produces outer membrane protein A (OmpA)-like proteins (OmpALPs), Pgm6 and Pgm7, as major O-linked glycoproteins. They resemble members of the OmpA family in their C-terminal domain that protrudes in the periplasmic space. The N-terminal membrane anchor domain though does not show any significant sequence similarity. Two-dimensional, diagonal electrophoresis and chemical cross-linking experiments with or without a reducing agent clearly showed that these proteins mainly form stable heterotrimers via intermolecular disulfide bonds. It has been suggested that they play an important role in the integrity of the outer membrane and, similar to members of the Ompa family, are likely to function as a stabilizer of the cell wall rather than as a major porin in this organism.