This is a small family named after the porin fomA found n the outer membrane of Fusobacterium nucleatum. FomA is a trimeric protein, which exhibits channel properties similar to that of the other general porins. Deletions in the largest proposed external region (loop L6), made the fomA porins considerably more permeable to antibiotics, indicating larger pore channels. Results obtained from limited proteolysis of purified fomA, indicate that the N-terminal part of the protein is not an integral part of the ß-barrel, but forms a periplasmic domain instead, therefore the protein is proposed to form the ß-barrel distinct from the periplasmic N-terminal domain.