1.B.6 The OmpA-OmpF Porin (OOP) Family

The large OOP family includes the functionally well characterized OmpA porin of E. coli as well as the OmpF (OprF) porin of Pseudomonas aeruginosa (Baldermann et al., 1998). Both proteins contain an N-terminal 8 β-strand transmembrane domain and a cell surface C-terminal peptidoglycan-interaction domain (Grizot and Buchanan, 2004). Only this latter domain exhibits extensive sequence similarity with E. coli OmpA and M. tuberculosis OmpATb. OmpATb has been reported to be a low activity channel that is essential for adaptation of M. tuberculosis to low pH and survival in mouse macrophage, but channel activity has been questioned (Niederweis, 2003).OmpA proteins and their many homologues probably all form structures consisting of eight transmembrane, all next neighbor, antiparallel, amphipathic β-strands. They form small β-barrels with short turns at the periplasmic barrel ends, and long flexible loops at the external ends. A 1.65 Å resolution monomeric structure is available for the E. coli OmpA porin (Pautsch and Schulz, 2000). A tetrameric quarternary structure has been proposed in which the subunits of the tetramer dissociate relatively readily. However, monomeric structures are proposed for other members of this family (Gribun et al., 2004).

The OmpA family consists of heat-modifiable, surface-exposed, porin proteins that are in high-copy number in the outer membranes of many Gram-negative bacteria. OmpA proteins generally have  an N-terminal, eight-stranded, anti-parallel β barrel embedded in the outer membrane while the C-terminal domain is globular and located in the periplasmic space. Escherichia coli OmpA is the best characterized of the proteins, but homologues from pathogenic bacteria include Pseudomonas aeruginosa OprF, Haemophilus influenzae P5, Klebsiella pneumoniae OmpA, and Chlamydia trachomatis major outer membrane protein (MOMP). OmpA from the veterinary pathogens Mannheimia haemolytica, Haemophilus parasuis, Leptospira interrogans, and Pasteurella multocida have been studied to a lesser extent (Confer and Ayalew 2013). Among many of the pathogenic bacteria, OmpA proteins have important pathogenic roles including bacterial adhesion, invasion, or intracellular survival as well as evasion of host defenses or stimulators of pro-inflammatory cytokine production. These pathogenic roles are most commonly associated with central nervous system, respiratory and urogenital diseases. Additionally, OmpA family proteins can serve as targets of the immune system with immunogenicity related to surface-exposed loops of the molecule. In several cases, OmpA proteins are under evaluation as potential vaccine candidates (Confer and Ayalew 2013).

The P. aeruginosa OmpF (1.B.6.1.2) exists in two conformations: a minority single domain conformer and a majority two domain conformer (Sugawara et al., 2006). Only the former inserts into liposomes to give high conductance channel activity (Nestorovich et al., 2006). The active conformation is present only for short times (Nestorovich et al., 2006) accounting for low permeability reported previously.

The OOP family proteins may exhibit structural similarity with well-characterized virulence proteins such as the neisserial opacity (Opa) adhesins, the Salmonella Rck complement resistance protein, the Salmonella PagC intramacrophage survival protein, and the Yersinia Ail attachment/invasion protein (Baldermann et al., 1998). However, sequence similarity with these proteins is insufficient to establish homology. These protein β-barrels resemble those of the lipocalin family although the members of these two protein families serve entirely different functions and show no observable sequence similarity. OmpA of E. coli is required for bacterial conjugation and for maintenance of outer membrane stability.

Members of the Ail/Lom family of outer membrane proteins, which are homologous to OmpA of E. coli (1.B.6.1.2), provide protection from complement-dependent killing for a number of pathogenic bacteria. The Y. pestis KIM genome encodes four Ail/Lom family proteins. The Ail (Attachment inversion locus; 182aas) protein is essential for Y. pestis to resist complement-mediated killing. High-level expression of the three other Y. pestis Ail/Lom family proteins (the y1682, y2034, and y2446 proteins) provided no protection against complement-mediated bacterial killing (Bartra et al., 2008).

Intragenic duplication of the 8-stranded OmpX β-barrel produces a functional pore (Omp2X) the size of the OmpC porin (1.B.1.1.3) channel, a natural 16 stranded β-barrel (Arnold et al. 2007).  This provides a potential mechanism for generating larger porins of 16 TMSs from smaller porins of 8 TMSs.

This family belongs to the Outer Membrane Pore-forming Protein I (OMPP-I) Superfamily .



Arnold, T., M. Poynor, S. Nussberger, A.N. Lupas, and D. Linke. (2007). Gene duplication of the eight-stranded β-barrel OmpX produces a functional pore: a scenario for the evolution of transmembrane β-barrels. J. Mol. Biol. 366: 1174-1184.

Arora, A., D. Rinehart, G. Szabo, and L.K. Tamm. (2000). Refolded outer membrane protein A of Escherichia coli forms ion channels with two conductance states in planar lipid bilayers. J. Biol. Chem. 275: 1594-1600.

Baldermann, C., A. Lupas, J. Lubieniecki, and H. Engelhardt. (1998). The regulated outer membrane protein Omp21 from Comamonas acidovorans is identified as a member of a new family of eight-stranded β-sheet proteins by its sequence and properties. J. Bacteriol. 180: 3741-3749.

Bartra, S.S., K.L. Styer, D.M. O'Bryant, M.L. Nilles, B.J. Hinnebusch, A. Aballay, and G.V. Plano. (2008). Resistance of Yersinia pestis to complement-dependent killing is mediated by the Ail outer membrane protein. Infect. Immun. 76: 612-622.

Brinkman, F.S., M. Bains, and R.E.W. Hancock. (2000). The amino terminus of Pseudomonas aeruginosa outer membrane protein OprF forms channels in lipid bilayer membranes: correlation with a three-dimensional model. J. Bacteriol. 182: 5251-5255.

Brosig, A., J. Nesper, W. Boos, W. Welte, and K. Diederichs. (2009). Crystal structure of a major outer membrane protein from Thermus thermophilus HB27. J. Mol. Biol. 385: 1445-1455.

Cassin, E.K. and B.S. Tseng. (2019). Pushing beyond the envelope: the potential roles of OprF in biofilm formation and pathogenicity. J. Bacteriol. [Epub: Ahead of Print]

Chevalier, G., H. Duclohier, D. Thomas, E. Shechter, and H. Wróblewski. (1993). Purification and characterization of protein H, the major porin of Pasteurella multocida. J. Bacteriol. 175: 266-276.

Choi, C.H., E.Y. Lee, Y.C. Lee, T.I. Park, H.J. Kim, S.H. Hyun, S.A. Kim, S.K. Lee, and J.C. Lee. (2005). Outer membrane protein 38 of Acinetobacter baumannii localizes to the mitochondria and induces apoptosis of epithelial cells. Cell Microbiol 7: 1127-1138.

Confer, A.W. and S. Ayalew. (2013). The OmpA family of proteins: roles in bacterial pathogenesis and immunity. Vet Microbiol 163: 207-222.

Dabo, S.M., A. Confer, M. Montelongo, P. York, and J.H. Wyckoff, 3rd. (2008). Vaccination with Pasteurella multocida recombinant OmpA induces strong but non-protective and deleterious Th2-type immune response in mice. Vaccine 26: 4345-4351.

Dupont, M., E. Dé, R. Chollet, J. Chevalier, and J.M. Pagès. (2004). Enterobacter aerogenes OmpX, a cation-selective channel mar- and osmo-regulated. FEBS Lett. 569: 27-30.

Estrada Mallarino, L., E. Fan, M. Odermatt, M. Müller, M. Lin, J. Liang, M. Heinzelmann, F. Fritsche, H.J. Apell, and W. Welte. (2015). TtOmp85, a β-Barrel Assembly Protein, Functions by Barrel Augmentation. Biochemistry 54: 844-852.

Gao, T., L. Ju, J. Yin, and H. Gao. (2015). Positive regulation of the Shewanella oneidensis OmpS38, a major porin facilitating anaerobic respiration, by Crp and Fur. Sci Rep 5: 14263.

Giacani, L., S.L. Brandt, W. Ke, T.B. Reid, B.J. Molini, S. Iverson-Cabral, G. Ciccarese, F. Drago, S.A. Lukehart, and A. Centurion-Lara. (2015). Transcription of TP0126, Treponema pallidum putative OmpW homolog, is regulated by the length of a homopolymeric guanosine repeat. Infect. Immun. 83: 2275-2289.

Gribun, A., D.J. Katcoff, G. Hershkovits, I. Pechatnikov, and Y. Nitzan. (2004). Cloning and characterization of the gene encoding for OMP-PD porin: the major Photobacterium damsela outer membrane protein. Curr. Microbiol. 48: 167-174.

Gribun, A., Y. Nitzan, I. Pechatnikov, G. Hershkovits, and D.J. Katcoff. (2003). Molecular and structural characterization of the HMP-AB gene encoding a pore-forming protein from a clinical isolate of Actinetobacter baumannii. Curr. Microbiol. 47: 434-443.

Grizot, S. and S.K. Buchanan. (2004). Structure of the OmpA-like domain of RmpM from Neisseria meningitidis. Mol. Microbiol. 51: 1027-1037.

Hancock, R.E.W. and F.S.L. Brinkman. (2002). Function of Pseudomonas porins in uptake and efflux. Annu. Rev. Microbiol. 56: 17-38.

Hou, V.C., G.R. Moe, Z. Raad, T. Wuorimaa, and D.M. Granoff. (2003). Conformational epitopes recognized by protective anti-neisserial surface protein A antibodies. Infect. Immun. 71: 6844-6849.

Iida, A., Y. Ohnishi, and S. Horinouchi. (2008). An OmpA family protein, a target of the GinI/GinR quorum-sensing system in Gluconacetobacter intermedius, controls acetic acid fermentation. J. Bacteriol. 190: 5009-5019.

Iyer, R., S.H. Moussa, T.F. Durand-Réville, R. Tommasi, and A. Miller. (2018). Acinetobacter baumannii OmpA Is a Selective Antibiotic Permeant Porin. ACS Infect Dis 4: 373-381.

Jeanteur, D., J.H. Lakey, and F. Pattus. (1991). The bacterial porin superfamily: sequence alignment and structure prediction. Mol. Microbiol. 5: 2153-2164.

Jeanteur, D., J.H. Lakey, and F. Pattus. (1994). The porin superfamily: diversity and common features. In: Bacterial Cell Wall (Ghuysen, J.M. and R. Hakenbeck,eds.). Elsevier, Amsterdam, pp. 363-380.

Jyothisri, K., V. Deepak, and M.R. Rajeswari. (1999). Purification and characterization of a major 40 kDa outer membrane protein of Acinetobacter baumannii. FEBS Lett. 443: 57-60.

Khalid, S., P.J. Bond, T. Carpenter, and M.S. Sansom. (2008). OmpA: gating and dynamics via molecular dynamics simulations. Biochim. Biophys. Acta. 1778: 1871-1880.

Kleinschmidt, J.H. (2006). Folding kinetics of the outer membrane proteins OmpA and FomA into phospholipid bilayers. Chem Phys Lipids 141: 30-47.

Kleinschmidt, J.H. and L.K. Tamm. (1996). Folding intermediates of a β-barrel membrane protein. Kinetic evidence for a multi-step membrane insertion mechanism. Biochemistry 35: 12993-13000.

Maccarini, M., L. Gayet, J.P. Alcaraz, L. Liguori, B. Stidder, E.B. Watkins, J.L. Lenormand, and D.K. Martin. (2017). Functional Characterization of Cell-Free Expressed OprF Porin from Pseudomonas aeruginosa Stably Incorporated in Tethered Lipid Bilayers. Langmuir 33: 9988-9996.

Mahalakshmi R. and Marassi FM. (2008). Orientation of the Escherichia coli outer membrane protein OmpX in phospholipid bilayer membranes determined by solid-State NMR. Biochemistry. 47(25):6531-8.

Mahalakshmi, R., C.M. Franzin, J. Choi, and F.M. Marassi. (2007). NMR structural studies of the bacterial outer membrane protein OmpX in oriented lipid bilayer membranes. Biochim. Biophys. Acta. 1768: 3216-3224.

Marassi, F.M. (2011). Mycobacterium tuberculosis Rv0899 defines a family of membrane proteins widespread in nitrogen-fixing bacteria. Proteins 79: 2946-2955.

Mishra M., Ressler A., Schlesinger LS. and Wozniak DJ. (2015). Identification of OprF as a Complement Component C3 Binding Acceptor Molecule on the Surface of Pseudomonas aeruginosa. Infect Immun. 83(8):3006-14.

Molle, V., N. Saint, S. Campagna, L. Kremer, E. Lea, P. Draper, and G. Molle. (2006). pH-dependent pore-forming activity of OmpATb from Mycobacterium tuberculosis and characterization of the channel by peptidic dissection. Mol. Microbiol. 61: 826-837.

Nestorovich, E.M., E. Sugawara, H. Nikaido, and S.M. Bezrukov. (2006). Pseudomonas aeruginosa porin OprF: properties of the channel. J. Biol. Chem. 281: 16230-16237.

Niederweis, M. (2003). Mycobacterial porins – new channel proteins in unique outer membranes. Mol. Microbiol. 49: 1167-1177.

Nikaido, H. (1992). Porins and specific channels of bacterial outer membranes. Mol. Microbiol. 6: 435-442.

Pautsch, A. and G.E. Schulz. (2000). High-resolution structure of the OmpA membrane domain. J. Mol. Biol. 298: 273-282.

Poppleton, D.I., M. Duchateau, V. Hourdel, M. Matondo, J. Flechsler, A. Klingl, C. Beloin, and S. Gribaldo. (2017). Outer Membrane Proteome of A Diderm Firmicute of the Human Microbiome. Front Microbiol 8: 1215.

Raterman, E.L., D.D. Shapiro, D.J. Stevens, K.J. Schwartz, and R.A. Welch. (2013). Genetic analysis of the role of yfiR in the ability of Escherichia coli CFT073 to control cellular cyclic dimeric GMP levels and to persist in the urinary tract. Infect. Immun. 81: 3089-3098.

Renault, M., O. Saurel, J. Czaplicki, P. Demange, V. Gervais, F. Löhr, V. Réat, M. Piotto, and A. Milon. (2009). Solution state NMR structure and dynamics of KpOmpA, a 210 residue transmembrane domain possessing a high potential for immunological applications. J. Mol. Biol. 385: 117-130.

Renault, M., O. Saurel, P. Demange, V. Reat, and A. Milon. (2010). Solution-state NMR spectroscopy of membrane proteins in detergent micelles: structure of the Klebsiella pneumoniae outer membrane protein A, KpOmpA. Methods Mol Biol 654: 321-339.

Saint, N., C. El Hamel, E. Dé, and G. Molle. (2000). Ion channel formation by N-terminal domain: a common feature of OprFs of Pseudomonas and OmpA of Escherichia coli. FEMS Microbiol. Lett. 190: 261-265.

Schulz, G.E. (1996). Porins: general to specific, native to engineered passive pores. Curr. Opin. Struc. Biol. 6: 485-490.

Senaratne, R.H., J. Mobasheri, K.G. Papavinasasundaram, P. Jenner, E.D.A. Lea, and P. Draper. (1998). Expression of a gene for a porin-like protein of the OmpA family from Mycobacterium tuberculosis H37Rv. J. Bacteriol. 180: 3541-3547.

Song, H., J. Huff, K. Janik, K. Walter, C. Keller, S. Ehlers, S.H. Bossmann, and M. Niederweis. (2011). Expression of the ompATb operon accelerates ammonia secretion and adaptation of Mycobacterium tuberculosis to acidic environments. Mol. Microbiol. 80: 900-918.

Stancik, L.M., D.M. Stancik, B. Schmidt, D.M. Barnhart, Y.N. Yoncheva, and J.L. Slonczewski. (2002). pH-dependent expression of periplasmic proteins and amino acid catabolism in Escherichia coli. J. Bacteriol. 184: 4246-4258.

Sugawara, E. and H. Nikaido. (1992). Pore-forming activity of OmpA protein of Escherichia coli. J. Biol. Chem. 267: 2507-2511.

Sugawara, E. and H. Nikaido. (1994). OmpA protein of Escherichia coli outer membrane occurs in open and closed channel forms. J. Biol. Chem. 269: 17981-17987.

Sugawara, E. and H. Nikaido. (2012). OmpA is the principal nonspecific slow porin of Acinetobacter baumannii. J. Bacteriol. 194: 4089-4096.

Sugawara, E., E.M. Nestorovich, S.M. Bezrukov, and H. Nikaido. (2006). Pseudomonas aeruginosa porin OprF exists in two different conformations. J. Biol. Chem. 281: 16220-16229.

Sugawara, E., K. Nagano, and H. Nikaido. (2010). Factors affecting the folding of Pseudomonas aeruginosa OprF porin into the one-domain open conformer. MBio 1:.

Sugawara, E., M. Steiert, S. Rouhani, and H. Nikaido. (1996). Secondary structure of the outer membrane proteins OmpA of Escherichia coli and OprF of Pseudomonas aeruginosa. J. Bacteriol. 178: 6067-6069.

Teriete, P., Y. Yao, A. Kolodzik, J. Yu, H. Song, M. Niederweis, and F.M. Marassi. (2010). Mycobacterium tuberculosis Rv0899 Adopts a Mixed alpha/β-Structure and Does Not Form a Transmembrane β-Barrel. Biochemistry 49: 2768-2777.

Vashist, J. and M.R. Rajeswari. (2006). Structural investigations on novel porin, OmpAb from Acinetobacter baumannii. J Biomol Struct Dyn 24: 243-253.

Verma, S., R. Salwan, S. Katoch, L. Verma, R. Chahota, P. Dhar, and M. Sharma. (2016). The relationship between capsular type and OmpA of Pasteurella multocida is associated with the outcome of disease. Microb. Pathog. 101: 68-75. [Epub: Ahead of Print]

Veyron-Churlet, R., B. Brust, L. Kremer, and A.B. Blanc-Potard. (2011). Expression of OmpATb is dependent on small membrane proteins in Mycobacterium bovis BCG. Tuberculosis (Edinb) 91: 544-548.

Walzer, G., E. Rosenberg, and E.Z. Ron. (2006). The Acinetobacter outer membrane protein A (OmpA) is a secreted emulsifier. Environ Microbiol 8: 1026-1032.

White, P.A., S.P. Nair, M.J. Kim, M. Wilson, and B. Henderson. (1998). Molecular characterization of an outer membrane protein of Actinobacillus actinomycetemcomitans belonging to the OmpA family. Infect. Immun. 66: 369-372.

Yang, Y., D. Auguin, S. Delbecq, E. Dumas, G. Molle, V. Molle, C. Roumestand, and N. Saint. (2011). Structure of the Mycobacterium tuberculosis OmpATb protein: a model of an oligomeric channel in the mycobacterial cell wall. Proteins 79: 645-661.

Zhao, X., Y. Cui, Y. Yan, Z. Du, Y. Tan, H. Yang, Y. Bi, P. Zhang, L. Zhou, D. Zhou, Y. Han, Y. Song, X. Wang, and R. Yang. (2013). Outer membrane proteins ail and OmpF of Yersinia pestis are involved in the adsorption of T7-related bacteriophage Yep-phi. J. Virol. 87: 12260-12269.

Zhou J., Wang K., Xu S., Wu J., Liu P., Du G., Li J. and Chen J. (2015). Identification of membrane proteins associated with phenylpropanoid tolerance and transport in Escherichia coli BL21. J Proteomics. 113:15-28.


TC#NameOrganismal TypeExample

Weakly anion-selective OmpA porin.  Can exist in two distinct conductance states (Arora et al. 2000).  May function in the transport of phenylpropanoids (resveratrol, naringenin and rutin) (Zhou et al. 2014). Three membrane-bound folding intermediates of OmpA were discovered in folding studies with dioleoylphosphatidylcholine bilayers. A highly synchronized mechanism of secondary and tertiary structure formation, applicable to this and other β-barrel membrane proteins has been described (Kleinschmidt 2006).


OmpA of E. coli (P0A910)


Outer membrane insertion signal domain protein of 190 aas and one N-terminal TMS.  An ortholog in Veillonella parvula is 84% identical, and was considered to be a porin by Poppleton et al. 2017.


OMISD protein of Veillonella atypica


OmpA of 210 aas. The 3-d structure has been solved by NMR (Renault et al. 2010), and its dynamics have been examined (Renault et al. 2009).

Gram-negative bacteria

OmpA of Klebsiella pneumoniae


Omp34 outer membrane porin of 346 aas.  Also known as the Major antigen Fc binding protein (White et al. 1998).


Omp34 of Aggregatibacter actinomycetemcomitans (Actinobacillus actinomycetemcomitans) (Haemophilus actinomycetemcomitans)


Putative porin of 253 aas


Putative porin of Nocardioidaceae bacterium Broad-1


Outer membrane protein of 638 aas, OmpF


OmpF of Cecembia lonarensis




OmpA/F of Treponema pallidum


OmpA family porin of 410 aas


OmpA porin of Phenylobacterium zucineum


Putative OmpF homologue


Putative OmpF homologue of Leptospira interrogans


Outer membrane protein of 210 aas and 8 putative TMSs


OMP of Thiothrix nivea


Outer membrane protein of 218 aas and 8 putative TMSs


OMP of Mariniradius saccharolyticus


OmpF (OprF) porin.  The N-terminal domain has pore activity (Saint et al. 2000).  The protein can exist in multiple conformations of variable conductivities (Nestorovich et al. 2006).  Factors affecting its one-domain open conformer have been studied by Sugawara et al. (2010). OprF is a complement component C3 receptor (Mishra et al. 2015) and is a target of antibacterial drugs (Maccarini et al. 2017). OprF assumes dual conformations and is involved in solute transport, cell envelope integrity, biofilm formation and pathogenesis (Cassin and Tseng 2019).


OmpF (OprF) of Pseudomonas aeruginosa (P13794)


OmpA homologue of 189 aas


OmpA homologue of Leptospira biflexa


OmpA-type porin of 160 aas, YfiB The yfiRNB locus in E. coli CFT073 contains genes for YfiN, a diguanylate cyclase, and its activity regulators, YfiR and YfiB.(Raterman et al. 2013).

YfiB of E. coli


Constitutively expressed OmpA of 365 aas (Gao et al. 2015).

OmpA of Shewanella oneidensis


OmpA of 354 aas with 1 N-terminal α-TMS, 10 putative β-TM Strands and a periplasmic C-terminal domain, probably a peptidoglycan-binding domain (Khalid et al. 2008).  Plays a role in virulence (pneumonia in pigs and ruminants) (Verma et al. 2016; Confer and Ayalew 2013) and has been used for vaccine development (Dabo et al. 2008).

OmpA of Pasteurella multocida


Omp38; OmpA of 356 aas and 1 N-terminal TMSs. It is a selective antibiotic transporting porin (Iyer et al. 2018; Jyothisri et al. 1999) and induces apoptosis in human cell lines through caspase-dependent and AIF-dependent pathways. Purified Omp38 enters host cells and localizes to the mitochondria, which presumably leads to a release of proapoptotic molecules such as cytochrome c and AIF (apoptosis-inducing factor) (Choi et al. 2005).

omp38 of Acinetobacter baumannii


Putative OmpA porin of 345 aas and one N-terminal TMS. Its gene is adjacent to an autoinducer exporter-like protein (2.A.86.1.11) (Poppleton et al. 2017).

OmpA-like protein of Veillonella parvula


OmpATb (ArfA). The central domain (residues 73-220) has been reported to exhibit channel activity (Molle et al., 2006). Its expression is dependent on small single TMS membrane proteins which are encoded in a single operon with it (Veyron-Churlet et al., 2011). The rv0899 gene, encoding OmpATb, is part of an operon (rv0899-rv0901) that is required for fast ammonia secretion, pH neutralization, and growth of M. tuberculosis in acidic environments (Song et al. 2011). Homologues are widespread in bacteria with functions in nitrogen metabolism, adaptation to nutrient poor environments, and/or establishing symbiosis with host organisms (Marassi, 2011). The high resolution 3-d structure is known, revealing two independent domains separated by a proline-rich hinge region.The C-terminal domain (OmpATb(198-326)) revealed a module structurally related to other OmpA-like proteins from Gram-negative bacteria, but the N-terminal domain(73-204), which  forms channels in planar lipid bilayers, exhibits a fold, which belongs to the α+β sandwich class fold. It exists in a major monomeric form and a minor oligomeric form yielding rings able to insert into phospholipid membranes (Yang et al. 2011).


OmpATb of Mycobacterium tuberculosis (P65593)


HMP-AB outer membrane porin, OmpAb or Omp38 (Gribun et al., 2004).  It is the principle porin with an inner diameter of 2 nm which allows transport of cephalothin, cephaloridine, other antibiotics as well as other small molecules across the outer membrane (Sugawara and Nikaido 2012). Structural studies have been reported (Vashist and Rajeswari 2006). It is a secreted emulifier in some strains of Acinetobacter (Walzer et al. 2006). The sequence provided may be slightly incorrect (see the Q6BYW5 sequence of 356 aas).


HMP-AB of Acinetobacter baumannii (Q8KWW6)


The OmpA-OmpF porin (OOP) family member, GmpA (involved in acetic acid fermentation; under quorum sensing control) (Iida et al., 2008). (most similar to 1.B.6.1.4)


GmpA of Gluconacetobacter intermedius (B3A000)

1.B.6.1.6Outer membrane protein 40 (Omp40) (PG33)BacteriaPG_0694 of Porphyromonas gingivalis

OmpA homologue

Firmicute with outer membrane

OmpA homologue of Megasphaera elsdenii


OmpA homologue

Firmicute with outer membrane

OmpA homologue of Megasphaera sp. UPII 135-E


OMP_b-br1 family protein

Firmicute with outer membrane

Outer membrane protein of Megasphaera elsdenii


TC#NameOrganismal TypeExample

Putative OmpW homologue of 219 aas (Giacani et al. 2015).


Putative OmpW homologue of Treponema pallidum


Putative OmpW homologue of 291 aas (Giacani et al. 2015).


Putative OmpW homologue of Treponema pallidum


Putative OmpW porin of 211 aas and 8 β-strands


Putative OmpW homologue of Treponema azotonutricium


Putative OmpW homologue of 206 aas and 8 β-strands.


Putative OmpW homologue of Spirochaeta africana


Putative OmpW homologue of 211 aas


OmpW homologue of Borrelia hermsii


Uncharacterized protein of 196 aas.


UP of Sphaerochaeta pleomorpha


Uncharacterized protein of 205 aas.


UP of Treponema denticola


TC#NameOrganismal TypeExample

Putative porin of 357 aas and 1 N-terminal TMS

Porin of Candidatus Methanoperedenaceae archaeon


TC#NameOrganismal TypeExample

Outer membrane porin precursor, OmpX (8 TM β-strands) (NMR structures in lipid bilayers solved (Mahalakshmi et al., 2007; Mahalakshmi and Marassi, 2008)). Expression of the gene is induced by acid or base compared to pH 7 (Stancik et al. 2002).


OmpX of E. coli (P0A917)


Outer membrane porin, OmpX of 171 aas (Dupont et al. 2004).


OmpX of Enterobacter (Aerobacter) aerogenes


Outer membrane porin, opacity type, of 189 aas


OMP of Prosthecochloris vibrioformis


Outer membrane porin, opacity type, of 230 aas


OMP of Chlorobaculum parvum


Putative invasin of 242 aas


Putative invasin of E. coli


Uncharacterized protein of 290 aas


UP of Nitrobacter hamburgensis


Putative porin of 199 aas


Putative porin of Rhodanobacter thiooxydans


Uncharacterized protein of 196 aas


UP of Vibrio fischeri


Putative porin of 195 aas


Putative porin of Vibrio alginolyticus


Uncharacterized protein of 186 aas


UP of Agarivorans albus


Putative porin of 182 aas


PP of Grimontia hollisae


The attachment inversion locus (Ail) (Bartra et al., 2007).  Membrane-bound proteins, Ail and OmpF, are involved in the adsorption of T7-related bacteriophage (Zhao et al. 2013).


Ail of Yersinia pestis (Q0WCZ9)


Ail/Lom protein of 199 aas

Ail/Lom protein of E. coli

1.B.6.2.3Opacity family porin protein

Gram-negative bacterium

UMN179_00549 of Gallibacterium anatis
1.B.6.2.4Opacity family porin protein

Gram-negative bacterium

UMN179_00948 of Gallibacterium anatis

Neisserial surface protein A, NspA of 174 aas and 8 TMSs (Hou et al. 2003).


NspA of Neisseria meningitidis

1.B.6.2.6Porin opacity typeNoneAM202_02155 of Actinobacillus minor 202
1.B.6.2.7Arginine transporter permease subunit ArtMNoneGGC_0882 of Haemophilus haemolyticus M21621
1.B.6.2.8Opa-like protein ANoneE9U_09445 of Moraxella catarrhalis BC8
1.B.6.2.9Surface protein ANone

NspA of Neisseria wadsworthii 9715


TC#NameOrganismal TypeExample

Putative porin of 197 aas


PP of Opitutaceae bacterium TAV1


Putative porin of 277 aas


PP of Coraliomargarita sp. CAG:312


Putative porin


PP of Opitutus terrae


TC#NameOrganismal TypeExample

Putative porin of 183 aas


Putative porin of Vibrio parahaemolyticus


Porin of 190 aas and 1 N-terminal TMS.

Porin of Shewanella psychrophila


Porin of 198 aas and 1 N-terminal TMS.

Porin of Pseudoalteromonas luteoviolacea


Porin of 180 aas and 1 N-terminal TMS

Porin of Vibrio caribbeanicus


Porin of 186 aas and 1 N-terminal TMS

Porin of Litorilituus sp. RZ04


TC#NameOrganismal TypeExample

Outer membrane protein of 205 aas and 8 putative TMSs.


OMP of Fibrobacter succinogens


Outer membrane protein of 197 aas and 8 putative TMSs.


OMP of Fibrobacter succinogenes


Outer membrane protein of 534 aas and 6 - 22 beta strands.


OMP of Turneriella parva


Outer membrane protein of 211 aas and 8 beta strands.


OMP of Myxococcus xanthus


Outer membrane protein of 201 aas and 9 putative beta strands.


OMP of Vibrio tubiashii


Outer membrane protein, OmpA of 196 aas and 8 putative TMSs


OmpA of Aliivibrio salmonicida


TC#NameOrganismal TypeExample

Outer membrane protein of 201 aas and 8 putative β-TMSs.


OMP of Cyclobacterium marinum


Putative porin of 157 aas and 8 beta strands


Putative porin of Paludibacter propionicigenes


Uncharacterized protein of 208 aas.


UP of Pedobacter saltans


Putative porin of 192 aas


Putative porin of Capnocytophaga sputigena


Outer membrane protein of 224 aas and 8 TMSs


OMP of Dyadobacter fermentans


Outer membrane protein of 204 aas and 8 TMSs


OMP of Solitalea canadensis


Outer membrane protein of 221 aas and 8 TMSs


OMP of Psychroflexus torquis


Outer membrane protein of 222 aas


OMP of Echinicola vietnamensis


Outer membrane protein of 199 aas


OMP of Chitinophaga pinensis


Porin of 193 aas and 8 beta strands


Porin of Flavobacterium johnsoniae


Porin of 180 aas and 8 beta strands


Porin of Candidatus Nitrospira defluvii


Porin of 207 aas and 8 beta strands


Porin of Myxococcus xanthus


TC#NameOrganismal TypeExample

Outer membrane protein of 257 aas and 8 beta strands


OMP of Bacteroides fragilis


Porin of 275 aas and 1 N-terminal TMS

Porin of Bacteroides xylanisolvens


DUF4421 domain-containing protein of 334 aas and 1 N-terminal TM

Putative porin of Flavobacterium rivuli


TC#NameOrganismal TypeExample

Porin of 224 aas and 8 beta strands, TtoA (Estrada Mallarino et al. 2015).  The crystal structure is known (3DZM) (Nesper et al. 2008). The 2.8 Å structure reveals a transmembrane 8 stranded β-barrel, an extracellular cation-binding region and an external 5-β stranded sheet (Brosig et al. 2009).


Porin of Thermus thermophilus


Putative porin of 222 aas.


Putative porin of Deinococcus geothermalis


Putative porin of 227 aas and 1 N-terminal TMS

Porin of Ignavibacterium album


TC#NameOrganismal TypeExample

Uncharacterized protein of 186 aas.


UP of Ignavibacterium album


Uncharacterized putative porin protein of 189 aas.


UP of Owenweeksia hongkongensis


Uncharacterized putative porin of 205 aas


Putative porin of Owenweeksia hongkongensis


Uncharacterized protein of 167 aas


UP of Elizabethkingia anophelis