| 1.B.3 The Sugar Porin (SP) Family
The SP family includes the well characterized maltoporin of E. coli for which the three-dimensional structures with and without its substrate have been obtained by X-ray diffraction. The protein consists of an 18 β-stranded β-barrel in contrast to proteins of the general bacterial porin family (GBP) and the Rhodobacter PorCa Porin (RPP) family which consist of 16 β-stranded &beta-barrels. Although maltoporin contains a wider beta-barrel than the porins of the GBP and RPP families (TC#s 1.B.1 and 1.B.7), it exhibits a narrower channel, showing only 5% of the ionic conductance of the latter porins.
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This family belongs to the Outer Membrane Pore-forming Protein I (OMPP-I) Superfamily .
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| References: |
Andersen, C., B. Rak, and R. Benz. (1999). The gene bglH present in the bgl operon of Escherichia coli, responsible for uptake and fermentation of β-glucosides encodes for a carbohydrate-specific outer membrane porin. Mol. Microbiol. 31: 499-510.
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Anderson, D.M., K.M. Anderson, C.L. Chang, C.A. Makarewich, B.R. Nelson, J.R. McAnally, P. Kasaragod, J.M. Shelton, J. Liou, R. Bassel-Duby, and E.N. Olson. (2015). A micropeptide encoded by a putative long noncoding RNA regulates muscle performance. Cell 160: 595-606.
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Dutzler, R., Y.F. Wang, P.J. Rizkallah, J.P. Rosenbusch and T. Schirmer (1996). Crystal structures of various maltooligosaccharides bound to maltoporin reveal a specific sugar translocation pathway. Structure 4: 127-134.
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Gerken, H., D. Shetty, B. Kern, L.J. Kenney, and R. Misra. (2024). Effects of pleiotropic and alleles of on envelope stress and antibiotic sensitivity. J. Bacteriol. 206: e0017224.
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Hardesty, C., C. Ferran and J.M. DiRenzo (1991). Plasmid-mediated sucrose metabolism in Escherichia coli: characterization of scrY, the structural gene for a phosphoenolpyruvate-dependent sucrose phosphotransferase system outer membrane porin. J. Bacteriol. 173: 449-456.
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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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Kim, B.H., C. Andersen, J. Kreth, C. Ulmke, K. Schmid, and R. Benz. (2002). Site-directed mutagenesis within the central constriction site of ScrY (sucroseporin): effect on ion transport and comparison of maltooligosaccharide binding to LamB of Escherichia coli. J. Membr. Biol. 187: 239-253.
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Lin, X.M., M.J. Yang, H. Li, C. Wang, and X.X. Peng. (2014). Decreased expression of LamB and Odp1 complex is crucial for antibiotic resistance in Escherichia coli. J Proteomics 98: 244-253.
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Löwe, H., P. Sinner, A. Kremling, and K. Pflüger-Grau. (2018). Engineering sucrose metabolism in Pseudomonas putida highlights the importance of porins. Microb Biotechnol. [Epub: Ahead of Print]
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Meyer, J.E.W., M. Hofnung and G.E. Schulz (1997). Structure of maltoporin from Salmonella typhimurium ligated with a nitrophenyl-maltotrioside. J. Mol. Biol. 266: 761-775.
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Mulvihill, E., M. Pfreundschuh, J. Thoma, N. Ritzmann, and D.J. Müller. (2019). High-Resolution Imaging of Maltoporin LamB while Quantifying the Free-Energy Landscape and Asymmetry of Sugar Binding. Nano Lett. [Epub: Ahead of Print]
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Nelson, B.R., C.A. Makarewich, D.M. Anderson, B.R. Winders, C.D. Troupes, F. Wu, A.L. Reese, J.R. McAnally, X. Chen, E.T. Kavalali, S.C. Cannon, S.R. Houser, R. Bassel-Duby, and E.N. Olson. (2016). Muscle physiology. A peptide encoded by a transcript annotated as long noncoding RNA enhances SERCA activity in muscle. Science 351: 271-275.
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Nikaido, H. (1992). Porins and specific channels of bacterial outer membranes. Mol. Microbiol. 6: 435-442.
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Schirmer, T., T.A. Keller, Y.F. Wang and J.P. Rosenbusch (1995). Structural basis for sugar translocation through maltoporin channels at 3.1 Å resolution. Science 267: 512-514.
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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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Sun, L., F. Bertelshofer, G. Greiner, and R.A. Böckmann. (2016). Characteristics of Sucrose Transport through the Sucrose-Specific Porin ScrY Studied by Molecular Dynamics Simulations. Front Bioeng Biotechnol 4: 9.
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Wang, Y.F., R. Dutzler, P.J. Rizkallah, J.P. Rosenbusch and T. Schirmer (1997). Channel specificity: structural basis for sugar discrimination and differential flux rates in maltoporin. J. Mol. Biol. 272: 56-63.
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| Examples: |
| TC# | Name | Organismal Type | Example |
| 1.B.3.1.1 | LamB (MalL) maltoporin (maltose–maltoheptose). Also catalyzes the uptake of antibiotics (Lin et al. 2014). LamB preferentially binds maltodextrins from the periplasmic side, and thus, sugar binding and uptake are asymmetric (Mulvihill et al. 2019). Expression of the lamB gene is regulated by EnvZ and OmpR in response to osmolarity and thereby influences antibiotic resistance (Gerken et al. 2024). | Bacteria | LamB of E. coli |
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| 1.B.3.1.10 | Uncharacterized protein | Nitrospira | Putative porin of Candidatus Nitrospira defluvii |
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| 1.B.3.1.11 | Putative porin of 385 aas | Planctomycetes | Porin of Planctomycete KSU-1 |
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| 1.B.3.1.12 | Putative porin of 447 aas | Verrucomicrobia | PP of Pedosphaera parvula |
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| 1.B.3.1.13 | sucrose porin, ScrY, of 521 aas (Löwe et al. 2018). | | ScrY of Pseudomonas putida |
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| 1.B.3.1.14 | Maltoporin, LamB; MalL, of 439 aas and 1 -terminal TMS. | | LamB of Aeromonas veronii |
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| 1.B.3.1.2 | Oligosaccharide porin, ScrY (transports sucrose, raffinose and maltooligo-saccharides) (Kim et al. 2002). The 3-d structure known (PDB ID 1A0S). Sucrose translocation through the pore showed two main energy barriers within the
constriction region of ScrY. Three asparate residues are key
residues, opposing the passage of sucrose, all located within the L3 loop (Sun et al. 2016). | Bacteria | ScrY of Salmonella typhimurium |
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| 1.B.3.1.3 | Porin with specificity for β-glucosides, BglH of 538 aas. High affinity binding was observed with the aromatic beta-D-glucosides
arbutin and salicin as well as with gentibiose and cellobiose. Binding of
maltooligosaccharides to BglH was much weaker, indicating that the binding site of BglH for carbohydrates is different from that of LamB (maltoporin) (Andersen et al. 1999). | Bacteria | BglH (YieC) of E. coli |
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| 1.B.3.1.4 | Maltoporin | Gram-negative bacteria | LamB of Alteromonas sp. |
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| 1.B.3.1.5 | Outer membrane porin homologue | γ-Proteobacteria | Omp of Glaciecola mesophila (K6YXR7) |
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| 1.B.3.1.6 | Putative outer membrane porin | γ-Proteobacteria | Omp of Rheinheimera nanhaiensis (I1DXN7) |
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| 1.B.3.1.7 | Putative outer membrane porin | Aquifacae | OMP of Aquifex aeolicus (O67300) |
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| 1.B.3.1.8 | Putative porin | Proteobacteria | Porin of Chromohalobacter salexigens |
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| 1.B.3.1.9 | Putative porin | Verrucomicrobia | Porin of Verrucomicrobiae bacterium |
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| Examples: |
| TC# | Name | Organismal Type | Example |
| 1.B.3.2.1 | Putative porin of 411 aas | Verrucomicrobia | PP of Opitutus terrae |
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| 1.B.3.2.2 | Putative porin of 397 aas | Proteobacteria | PP of Thioflavicoccus mobilis |
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| 1.B.3.2.3 | Putative porin of 401 aas | Proteobacteria | PP of Marinobacter aquaeolei (Marinobacter hydrocarbonoclasticus) |
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| 1.B.3.2.4 | Uncharacterized protein of 355 aas and 1 N-terminal TMS. | | UP of Vibrio celticus |
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| Examples: |
| TC# | Name | Organismal Type | Example |
| 1.B.3.3.1 | Uncharacterized putative porin of 448 aas | | UP of Bdellovibrio bacteriovorus |
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