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1.B.32 The Fusobacterial Outer Membrane Porin (FomA) Family

FomA is the designation given to a small family of sequence similar outer membrane porins from F. nucleatum. They are trimeric proteins, each subunit exhibiting 14 C-terminal antiparallel transmembrane β-strands connected to an N-terminal periplasmic domain (Puntervoll et al., 2002). An external loop, L6, the largest of the seven such loops, when deleted renders FomA more permeable to antibiotics. L6 probably folds back into the β-barrel, thereby constricting the pore. FomA porins lack significant sequence similarity to other known porins, but they do exhibit similar structural features. They transport solutes non-specifically except for a size limit. Deletion of L6 increases this size limit.

The transport reaction catalyzed by FomA porins is:

solute (out) solute (periplasm)

References associated with 1.B.32 family:

Anbazhagan, V., N. Vijay, J.H. Kleinschmidt, and D. Marsh. (2008). Protein-lipid interactions with Fusobacterium nucleatum major outer membrane protein FomA: spin-label EPR and polarized infrared spectroscopy. Biochemistry 47: 8414-8423. 18642853
Kattner, C., S. Pfennig, P. Massari, and M. Tanabe. (2015). One-step purification and porin transport activity of the major outer membrane proteins P2 from Haemophilus influenzae, FomA from Fusobacterium nucleatum and PorB from Neisseria meningitidis. Appl Biochem Biotechnol 175: 2907-2915. 25575589
Kleinschmidt, J.H. (2006). Folding kinetics of the outer membrane proteins OmpA and FomA into phospholipid bilayers. Chem Phys Lipids 141: 30-47. 16581049
Kleivdal, H., P. Puntervoll, and H.B. Jensen. (2001). Topological investigation of the FomA porin from Fusobacterium nucleatum and identification of the constriction loop L6. Microbiology 147: 1059-1067. 11283301
Kleivdal, H., R. Benz, and H.B. Jensen. (1995). The Fusobacterium nucleatum major outer-membrane protein (FomA) forms trimeric, water-filled channels in lipid bilayer membranes. Eur J Biochem 233: 310-316. 7588760
Pszon-Bartosz, K., J.S. Hansen, K.B. Stibius, J.S. Groth, J. Emnéus, O. Geschke, and C. Hélix-Nielsen. (2011). Assessing the efficacy of vesicle fusion with planar membrane arrays using a mitochondrial porin as reporter. Biochem. Biophys. Res. Commun. 406: 96-100. 21295545
Puntervoll, P., H. Kleivdal, K. Ole Dahl, W. Bitter, J. Tommassen, and H.B. Jensen. (2000). The Fusobacterium nucleatum porin FomA possesses the general topology of the non-specific porins. Microbiology 146: 1437-1445. 10846222
Puntervoll, P., M. Ruud, L.J. Bruseth, H. Kleivdal, B.T. Høgh, R. Benz, and H.B. Jensen. (2002). Structural characterization of the fusobacterial non-specific porin FomA suggests a 14-stranded topology, unlike the classical porins. Microbiology 148: 3395-3403. 12427931