The porin RafY encoded by the raffinose plasmid pRSD2 of <i>Escherichia coli</i> forms a general diffusion pore and not a carbohydrate‐specific porin

Andersen, Christian; Krones, Daniela; Ulmke, Christine; Schmid, Kurt Werner; Benz, Roland

doi:10.1046/j.1432-1327.1998.2540679.x

Cited by 16 publications

(6 citation statements)

References 11 publications

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“…It is noteworthy also that general diffusion pores such as OmpF, OmpC, and the phosphate starvation-inducible PhoE close reversibly at low pH (14 -17). A similar effect has also been demonstrated for RafY and TolC with a more specific function (27,28). This channel closure has been explained in terms of protection of enteric bacteria against low pH environment when they pass through the digestive tract.…”

Section: Low Ph Closes the Maltoporin Channel In An Asymmetricsupporting

confidence: 70%

“…A similar behavior was observed with RafY, a pore-forming protein, which is part of the raf operon of E. coli plasmid pRSD2 and enables the uptake of raffinose across the outer membrane. Here, the trimeric nature of the outer membrane channel could be visualized at pH 6, where the monomers switched reversibly into closed configuration (27).…”

Section: Ph-induced Closure Of Maltoporin From E Colimentioning

confidence: 99%

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pH-induced Collapse of the Extracellular Loops ClosesEscherichia coli Maltoporin and Allows the Study of Asymmetric Sugar Binding

Andersen¹,

Schiffler²,

Charbit³

et al. 2002

Journal of Biological Chemistry

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LamB (maltoporin) is essential for the uptake of maltose and malto-oligosaccharides across the outer membrane of Escherichia coli. Purified LamB was reconstituted in artificial lipid bilayer membranes forming channels in the permanently open configuration at neutral pH. Almost complete channel closure was observed when the pH on both sides of the membrane was lowered to pH 4. When LamB was added to only one side of the membrane, the cis-side, and the pH was lowered at either side of the membrane, the cis-or the trans-side, the response to pH was asymmetric, suggesting preferential orientation of maltoporin channels and pHdependent closure of only one side of the channel. In experiments with LamB mutants in which major external loops L4, L6, and/or L9 were deleted, we identified the surface-exposed loops L4 and L6 as the cause of pH-mediated closure. The pH dependence of the LamB channel is consistent with the assumption that it inserts in a preferential orientation into the lipid bilayer. About 70 -80% of the reconstituted channels are oriented with the extracellular entrance toward the side to which the protein was added (the cis-side) and with the periplasmic opening on the opposite side (the trans-side). The possibility of closing the channels, which are oriented in the reverse direction by low pH at the trans-side, allowed the deduction of channel asymmetry with respect to carbohydrate binding kinetics. Whereas maltose binding was found to be almost symmetric with respect to the channel orientation, the sucrose and trehalose binding to LamB was asymmetric. The results are discussed in respect to possible physiological function of the pH-dependent closure of maltoporin.The outer membrane protects Gram-negative bacteria against noxious substances such as bile salts or degrading enzymes like proteinases or lipases (1, 2). Water-filled channels, the so-called porins, allow the passage of solutes through this diffusion barrier. Porins are divided in two classes: general diffusion pores, which sort solutes according to their molecular mass, and specific pores, which have a binding site for specific substrates inside the channel and facilitate the diffusion of these substrates through the outer membrane (3, 4). In the last few years the structure of several porins were solved by x-ray crystallography (5-7). Porins are built of three identical polypeptide subunits (monomers). The common structure of the monomers is a barrel formed by 16 or 18 antiparallel ␤-strands connected by small turns on the periplasmic side and by long loops on the extracellular side. In all known porin structures loop 3, between ␤-strands 5 and 6, is folded inside the channel and leads to a decrease in the diameter of the constriction of the channel. The other loops form a protrusion that protects the extracellular entrance of the outer membrane channels.LamB (maltoporin) from Escherichia coli is a specific porin for malto-oligosaccharides (8, 9). The monomer is composed of 18 ␤-strands, which means that there are nine extracellular loops. Th...

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Section: Low Ph Closes the Maltoporin Channel In An Asymmetricsupporting

confidence: 70%

Section: Ph-induced Closure Of Maltoporin From E Colimentioning

confidence: 99%

pH-induced Collapse of the Extracellular Loops ClosesEscherichia coli Maltoporin and Allows the Study of Asymmetric Sugar Binding

Andersen¹,

Schiffler²,

Charbit³

et al. 2002

Journal of Biological Chemistry

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“…One of the genes is rafY, which produces an OM channel (353). When RafY, a fairly large (50.7-kDa) protein that exists as a trimer, was inserted into a planar lipid bilayer, it produced a high single-channel conductance of 2.9 nS in 1 M KCl (16). Interestingly, however, there was no blocking of the channel by several sugars, including raffinose.…”

Section: Other Porinsmentioning

confidence: 99%

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

Nikaido

2003

Microbiol Mol Biol Rev

3,705

3,800

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Gram-negative bacteria characteristically are surrounded by an additional membrane layer, the outer membrane. Although outer membrane components often play important roles in the interaction of symbiotic or pathogenic bacteria with their host organisms, the major role of this membrane must usually be to serve as a permeability barrier to prevent the entry of noxious compounds and at the same time to allow the influx of nutrient molecules. This review summarizes the development in the field since our previous review (H. Nikaido and M. Vaara, Microbiol. Rev. 49:1-32, 1985) was published. With the discovery of protein channels, structural knowledge enables us to understand in molecular detail how porins, specific channels, TonB-linked receptors, and other proteins function. We are now beginning to see how the export of large proteins occurs across the outer membrane. With our knowledge of the lipopolysaccharide-phospholipid asymmetric bilayer of the outer membrane, we are finally beginning to understand how this bilayer can retard the entry of lipophilic compounds, owing to our increasing knowledge about the chemistry of lipopolysaccharide from diverse organisms and the way in which lipopolysaccharide structure is modified by environmental conditions

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“…coli maltoOMPP with 18 established β-TMSs [ 100 , 101 ] as well as the sucrose and β-glucoside OMPPs, and second, the much less well characterized Raffinose (RafY) Family (1.B.15), which includes the E . coli RafY OMPP that transports several oligosaccharides including the trisaccharide, raffinose [ 102 , 103 ]. The OMPPs of these two families have overlapping specificities for oligosaccharides, and they are closer to each other on the tree than to any other OMPP family.…”

Section: Resultsmentioning

confidence: 99%

Properties and Phylogeny of 76 Families of Bacterial and Eukaryotic Organellar Outer Membrane Pore-Forming Proteins

Reddy

Saier

2016

PLoS ONE

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We here report statistical analyses of 76 families of integral outer membrane pore-forming proteins (OMPPs) found in bacteria and eukaryotic organelles. 47 of these families fall into one superfamily (SFI) which segregate into fifteen phylogenetic clusters. Families with members of the same protein size, topology and substrate specificities often cluster together. Virtually all OMPP families include only proteins that form transmembrane pores. Nine such families, all of which cluster together in the SFI phylogenetic tree, contain both α- and β-structures, are multi domain, multi subunit systems, and transport macromolecules. Most other SFI OMPPs transport small molecules. SFII and SFV homologues derive from Actinobacteria while SFIII and SFIV proteins derive from chloroplasts. Three families of actinobacterial OMPPs and two families of eukaryotic OMPPs apparently consist primarily of α-helices (α-TMSs). Of the 71 families of (putative) β-barrel OMPPs, only twenty could not be assigned to a superfamily, and these derived primarily from Actinobacteria (1), chloroplasts (1), spirochaetes (8), and proteobacteria (10). Proteins were identified in which two or three full length OMPPs are fused together. Family characteristic are described and evidence agrees with a previous proposal suggesting that many arose by adjacent β-hairpin structural unit duplications.

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The porin RafY encoded by the raffinose plasmid pRSD2 of Escherichia coli forms a general diffusion pore and not a carbohydrate‐specific porin

Cited by 16 publications

References 11 publications

pH-induced Collapse of the Extracellular Loops ClosesEscherichia coli Maltoporin and Allows the Study of Asymmetric Sugar Binding

pH-induced Collapse of the Extracellular Loops ClosesEscherichia coli Maltoporin and Allows the Study of Asymmetric Sugar Binding

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

Properties and Phylogeny of 76 Families of Bacterial and Eukaryotic Organellar Outer Membrane Pore-Forming Proteins

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