| 1.B.7 The Rhodobacter PorCa Porin (RPP) Family
The Rhodobacter PorCa Protein, the only well characterized member of the RPP family, was the first porin to yield its three-dimensional structure by X-ray crystallography. It has a 16-stranded β-barrel structure similar to that of the members of the GBP (TC #1.B.1) family. Paupit et al. (1991) presented crystal structures of phosphoporin (PhoE; TC# 1.B.1.1.2), maltoporin (1.B.3.1.1; LamB) and Matrixporin (OmpF), all of E. coli, and found these have 3-d folds similar to that of the Rhodobacter porin, PorCa. It was not determined if this similarity is due to divergent evolution from a common ancestor or covergent evolution from dissimilar precursors. However, we have been able to demonstrate homology between members of families 1.B.1 and 1.B.7 using statistical means (M. Saier, unpublished results).
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This family belongs to the Outer Membrane Pore-forming Protein I (OMPP-I) Superfamily .
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| References: |
Burdman, S., R. De Mot, J. Vanderleyden, Y. Okon, and E. Jurkevitch. (2000). Identification and characterization of the omaA gene encoding the major outer membrane protein of Azospirillum brasilense. DNA Seq 11: 225-237.
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Jeanteur, D., J.H. Lakey and F. Pattus (1991). The bacterial porin superfamily: sequence alignment and structure prediction. Mol. Microbiol. 5: 2153-2164.
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Jeanteur, D., J.H. Lakey and F. Pattus (1994). The porin superfamily: diversity and common features. In: Bacterial Cell Wall. Edited by Ghuysen, J.M., Hakenbeck, R. Elsevier, Amsterdam, pp. 363-380.
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Kreusch, A. and G.E. Schultz (1994). Refined structure of the porin from Rhodopseudomonas blastica and comparison with the porin from Rhodobacter capsulatus. J. Mol. Biol. 243: 891-905.
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Moumène, A., I. Marcelino, M. Ventosa, O. Gros, T. Lefrançois, N. Vachiéry, D.F. Meyer, and A.V. Coelho. (2015). Proteomic Profiling of the Outer Membrane Fraction of the Obligate Intracellular Bacterial Pathogen Ehrlichia ruminantium. PLoS One 10: e0116758.
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Nikaido, H. (1992). Porins and specific channels of bacterial outer membranes. Mol. Microbiol. 6: 435-442.
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Pauptit, R.A., T. Schirmer, J.N. Jansonius, J.P. Rosenbusch, M.W. Parker, A.D. Tucker, D. Tsernoglou, M.S. Weiss, and G.E. Schultz. (1991). A common channel-forming motif in evolutionarily distant porins. J Struct Biol 107: 136-145.
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Saxena, K., O.M. Richter, B. Ludwig, and R. Benz. (1997). Molecular cloning and functional characterization of the Paracoccus denitrificans porin. Eur J Biochem 245: 300-306.
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Schiltz, E., A. Kreusch, U. Nestel and G.E. Schulz (1991). Primary structure of porin from Rhodobacter capsulatus. Eur. J. Biochem. 199: 587-594.
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Schulz, G.E. (1996). Porins: general to specific, native to engineered passive pores. Curr. Opin. Struc. Biol. 6: 485-490.
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Weiss, M.S., T. Wacker, J. Weckesser, W. Welte and G.E. Schulz (1990). The three-dimensional structure of porin from Rhodobacter capsulatus at 3 Å resolution. FEBS Lett. 267: 268-272.
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| Examples: |
| TC# | Name | Organismal Type | Example |
| 1.B.7.1.1 | PorCa (B10) porin. The 3-d structure is known (PDB ID 2POR). | Bacteria | PorCa porin of Rhodobacter capsulatus |
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| 1.B.7.1.2 | Paracoccus ion non-selective porin with 16 putative beta-strands, PorG (Saxena et al. 1997). | Bacteria | Porin of Paracoccus denitrificans |
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| 1.B.7.1.3 |
PorI (OpmA) porin. Forms channels that allow the passive diffusion of small hydrophilic solutes up to an exclusion limit of about 600 Da. The 3-d structure is known (PDB ID 1PRN). | Bacteria | PorI porin of Rhodobacter (Rhodopseudomonas) blastica |
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| 1.B.7.1.4 | OmaA major-porin (Burdman et al., 2000). | Gram-negative bacteria | OmaA of Azospirillum brasilense (Q9F9L3) |
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| 1.B.7.1.5 | Porin 41 (Por41) (Kleeberg, V., Neumann, U., Schultz, G.E. and Weckesser, J., unpublished) | Gram-negative bacteria | Por41 of Rhodospirillum rubrum (Q9K556) |
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| 1.B.7.1.6 | Outer membrane porin | Proteobacteria | SPO3430 of Silicibacter pomeroyi |
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| 1.B.7.1.7 | Putative porin of 332 aas | Proteobacteria | Putative porin of Rhodopseudomonas sphaeroides |
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| 1.B.7.1.8 | Porin of 385 aas (Moumène et al. 2015). | Proteobacteria | Porin of Ehrlichia ruminantium |
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| Examples: |
| TC# | Name | Organismal Type | Example |