1.B.39 The Bacterial Porin, OmpW (OmpW) Family

OmpW of Salmonella typhimurium has been shown to be required for the efficient efflux of methyl viologen and benzyl viologen (P. Youderian, personal communication). It functions in parallel with OmpD (NmpC in E. coli) which is the major Salmonella porin. OmpW is also the receptor for colicin S4. Homologues are found in many Gram-negative bacterial species including Pseudomonas, Azotobacter, Desulfitobacterium, Burkholderia, Xanthomonas, Rhodobacter, Ralstonia, Delftia and Rickettsia. One homologue is the major outer membrane protein, OprG of Pseudomonas aeruginosa (Gensberg et al., 1999). Another is the outer membrane protein, AlkL, probably involved in alkane transport (van Beilen et al., 1992).  An x-ray structure of OmpW has been presented (Albrecht et al. 2006). OmpW exhibits fast internal motion and residual conformational entropy (O'Brien et al. 2020).

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



Albrecht, R., K. Zeth, J. Söding, A. Lupas, and D. Linke. (2006). Expression, crystallization and preliminary X-ray crystallographic studies of the outer membrane protein OmpW from Escherichia coli. Acta Crystallogr Sect F Struct Biol Cryst Commun 62: 415-418.

Beketskaia, M.S., D.C. Bay, and R.J. Turner. (2014). Outer membrane protein OmpW participates with small multidrug resistance protein member EmrE in quaternary cationic compound efflux. J. Bacteriol. 196: 1908-1914.

Benz, R., M.D. Jones, F. Younas, E. Maier, N. Modi, R. Mentele, F. Lottspeich, U. Kleinekathöfer, and J. Smit. (2015). OmpW of Caulobacter crescentus Functions as an Outer Membrane Channel for Cations. PLoS One 10: e0143557.

Gensberg, K., A.W. Smith, F.S. Brinkman, and R.E. Hancock. (1999). Identification of oprG, a gene encoding a major outer membrane protein of Pseudomonas aeruginosa. J. Antimicrob. Chemother. 43: 607-608.

Giacani L., Brandt SL., Ke W., Reid TB., Molini BJ., Iverson-Cabral S., Ciccarese G., Drago F., Lukehart SA. and Centurion-Lara A. (2015). Transcription of TP0126, Treponema pallidum putative OmpW homolog, is regulated by the length of a homopolymeric guanosine repeat. Infect Immun. 83(6):2275-89.

Gil, F., F. Ipinza, J. Fuentes, R. Fumeron, J.M. Villarreal, A. Aspée, G.C. Mora, C.C. Vásquez, and C. Saavedra. (2007). The ompW (porin) gene mediates methyl viologen (paraquat) efflux in Salmonella enterica serovar typhimurium. Res. Microbiol. 158: 529-536.

Kucharska, I., P. Seelheim, T. Edrington, B. Liang, and L.K. Tamm. (2015). OprG Harnesses the Dynamics of its Extracellular Loops to Transport Small Amino Acids across the Outer Membrane of Pseudomonas aeruginosa. Structure 23: 2234-2245.

Ladkau, N., M. Assmann, M. Schrewe, M.K. Julsing, A. Schmid, and B. Bühler. (2016). Efficient production of the Nylon 12 monomer ω-aminododecanoic acid methyl ester from renewable dodecanoic acid methyl ester with engineered Escherichia coli. Metab Eng 36: 1-9. [Epub: Ahead of Print]

Neher, T.M. and D.R. Lueking. (2009). Pseudomonas fluorescens ompW: plasmid localization and requirement for naphthalene uptake. Can. J. Microbiol. 55: 553-563.

O''Brien, E.S., B. Fuglestad, H.J. Lessen, M.A. Stetz, D.W. Lin, B.S. Marques, K. Gupta, K.G. Fleming, and J.J. Wand. (2020). Membrane Proteins Have Distinct Fast Internal Motion and Residual Conformational Entropy. Angew Chem Int Ed Engl. [Epub: Ahead of Print]

Pilsl, H., D. Smajs, and V. Braun. (1999). Characterization of colicin S4 and its receptor, OmpW, a minor protein of the Escherichia coli outer membrane. J. Bacteriol. 181: 3578-3581.

Ritter A., Com E., Bazire A., Goncalves Mdos S., Delage L., Le Pennec G., Pineau C., Dreanno C., Compere C. and Dufour A. (2012). Proteomic studies highlight outer-membrane proteins related to biofilm development in the marine bacterium Pseudoalteromonas sp. D41. Proteomics. 12(21):3180-92.

Sanganna Gari, R.R., P. Seelheim, B. Marsh, V. Kiessling, C.E. Creutz, and L.K. Tamm. (2018). Quaternary structure of the small amino acid transporter OprG from Pseudomonas aeruginosa. J. Biol. Chem. [Epub: Ahead of Print]

Sullivan, J.T., S.D. Brown, and C.W. Ronson. (2013). The NifA-RpoN regulon of Mesorhizobium loti strain R7A and its symbiotic activation by a novel LacI/GalR-family regulator. PLoS One 8: e53762.

Touw, D.S., D.R. Patel, and B. van den Berg. (2010). The crystal structure of OprG from Pseudomonas aeruginosa, a potential channel for transport of hydrophobic molecules across the outer membrane. PLoS One 5: e15016.

van Beilen, J.B., G. Eggink, H. Enequist, R. Bos, and B. Witholt. (1992). DNA sequence determination and functional characterization of the OCT-plasmid-encoded alkJKL genes of Pseudomonas oleovorans. Mol. Microbiol. 6: 3121-3136.

Xiao, M., Y. Lai, J. Sun, G. Chen, and A. Yan. (2016). Transcriptional Regulation of the Outer Membrane Porin Gene ompW Reveals its Physiological Role during the Transition from the Aerobic to the Anaerobic Lifestyle of Escherichia coli. Front Microbiol 7: 799.


TC#NameOrganismal TypeExample

Outer membrane porin, OmpW.  Involved in paraquot efflux (Gil et al. 2007). OmpW also participates in the efflux of EmrE-specific substrates across the OM (Beketskaia et al. 2014). The 3-d structure is available (PDB#2F1C).


OmpW of Salmonella typhimurium


OCT plasmid-encoded AlkL outer membrane cation-selective porin, (probably transports alkanes) (van Beilen et al., 1992).  Has been used for the uptake of dodecanoic acid methyl ester (DAME) in E. coli for the production of  12-aminododecanoic acid methyl ester (ADAME), a building block for the high-performance polymer Nylon 12 (Ladkau et al. 2016).

Gram-negative bacteria

AlkL of Pseudomonas oleovorans (Q00595)


The anaerobically induced outer membrance porin, OprG. Transports small neutral amino acids (Kucharska et al. 2015). The 3-d structure is available (Touw et al. 2010).  Essential for normal biofilm formation (Ritter et al. 2012). It is an eight-stranded β-barrel monomer that is too narrow to accommodate even the smallest transported amino acid, glycine, raising the question of how OprG facilitates amino acid uptake (Sanganna Gari et al. 2018). Pro-92 of OprG is important for amino acid transport, with a P92A substitution inhibiting transport and the NMR structure of this variant revealing that this substitution produces structural changes in the barrel rim and restricts loop motions. OprG assembles into oligomers in the OM whose subunit interfaces could form a transport channel, and conformational changes in the barrel-loop region may be crucial for its activity (Sanganna Gari et al. 2018).

Gram-negative bacteria

OprG of Pseudomonas aeruginosa (Q9HWW1)

1.B.39.1.4The Naphthalene polycyclic aromatic hydrocarbon porin, OmpW (Neher and Lueking, 2009).

Gram-negative bacteria

OmpW of Pseudomonas fluorescens (Q3K638)


Porin of 230 aas; encoded within the  NifA-RpoN regulon and required for normal symbiosis. (Sullivan et al. 2013).


Porin of Mesorhizobium loti


Outer membrane porin, OmpW, of 212 aas.  Mediates transport of quaternary cationic ammonium compounds (Beketskaia et al. 2014).  It is involved in anaerobic carbon and energy metabolism, mediating the transition from aerobic to anaerobic lifestyles (Xiao et al. 2016).

OmpW of E. coli


Outer membrane porin selective for cations, OmpW of 226 aas (Benz et al. 2015).

OmpW of Caulobacter crescentus


Outer membrane porin of 214 aas, OmpW, selective for cations (Benz et al. 2015).

OmpW of Caulobacter crescentus


OmpW of 216 aas and 1 N-terminal TMS.

OmpW of Shewanella decolorationis


TC#NameOrganismal TypeExample

Putative outer membrane porin of 224 aas


OMP of Geobacter uraniireducens (Geobacter uraniumreducens)


Uncharacterized protein of 200 aas


UP of Geobacter daltonii