Crystal structures of various maltooligosaccharides bound to maltoporin reveal a specific sugar translocation pathway

Dutzler, Raimund; Wang, Y.F; Rizkallah, P.J.; Rosenbusch, J P; Schirmer, Tilman

doi:10.1016/s0969-2126(96)00016-0

Cited by 170 publications

(203 citation statements)

References 31 publications

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“…The saccharide-aromatics interactions have to be clarified for the analysis of the permeation process, because it makes a difference whether the observed ribbon of aromatic side chains were a continuous "greasy slide" (Dutzler et al, 1996), or a row of separated attracting patches. In the absence of sufficient physicochemical data, we performed a statistical analysis of the observed saccharide binding sites and converted it to interaction energies.…”

Section: G3-g2-g1mentioning

confidence: 99%

Energy profile of maltooligosaccharide permeation through maltoporin as derived from the structure and from a statistical analysis of saccharide‐protein interactions

Meyer

Schulz

1997

Protein Science

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The crystal structure of the maltodextrin-specific porin from Salmonella typhimurium ligated with a maltotrioside at the pore eyelet is known at 2.4 8, resolution. The three glucose units assume a conformation close to the natural amylose helix. The pore eyelet fits exactly the cross-section of a maltooligosaccharide chain and thus functions as a constraining orifice. The oligomer permeates the membrane by screwing along the amylose helix through this orifice. Because each glucose glides along the given helix, its interactions can be sampled at any point along the pathway. The interactions are mostly hydrogen bonds, but also contacts to aromatic rings at one side of the pore. We have derived the energy profile of a gliding maltooligosaccharide by following formation and breakage of hydrogen bonds and by assessing the saccharide-aromatics interactions from a statistical analysis of saccharide binding sites in proteins. The resulting profile indicates smooth permeation despite extensive hydrogen bonding at the orifice.

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Section: G3-g2-g1mentioning

confidence: 99%

Energy profile of maltooligosaccharide permeation through maltoporin as derived from the structure and from a statistical analysis of saccharide‐protein interactions

Meyer

Schulz

1997

Protein Science

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“…An even number of transmembrane b strands ranging from 8 to 22 has been observed in b-barrel membrane proteins of known crystal structure. Examples are the bacterial outer membrane proteins (OMPs), such as outer membrane protein A (OmpA) with 8 b strands (b-s) [5,6], OmpT (10 b-s) [7], OmPlA (12 b-s) [8], OmpF (16 b-s), maltose (LamB) [9,10] or sucrose (ScrY) [11] porins (18 b-s), and the iron transporters FhuA [12,13] or FepA [14] (22 b-s) (see fig. 1 for some examples).…”

Section: Introductionmentioning

confidence: 99%

Membrane protein folding on the example of outer membrane protein A of Escherichia coli

Kleinschmidt¹

2003

Cellular and Molecular Life Sciences (CMLS)

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Abstract. The biophysical principles and mechanisms by which membrane proteins insert and fold into a biomembrane have mostly been studied with bacteriorhodopsin and outer membrane protein A (OmpA). This review describes the assembly process of the monomeric outer membrane proteins of Gram-negative bacteria, for which OmpA has served as an example. OmpA is a two-domain outer membrane protein composed of a 171-residue eight-stranded b-barrel transmembrane domain and a 154-residue periplasmic domain. OmpA is translocated in an unstructured form across the cytoplasmic membrane into the periplasm. In the periplasm, unfolded OmpA is kept in solution in complex with the molecular chaperone Skp. After binding of periplasmic lipopolysaccharide, OmpA insertion and folding occur spontaneously upon interaction of the complex with the phospholipid bilayer. Insertion and folding of the b-barrel transmembrane domain into the lipid bilayer are highly synchronized, i.e. the formation of large amounts of b-sheet secondary structure and b-barrel tertiary structure take place in parallel with the same rate constants, while OmpA inserts into the hydrophobic core of the membrane. In vitro, OmpA can successfully fold into a range of model membranes of very different phospholipid compositions, i.e. into bilayers of lipids of different headgroup structures and hydrophobic chain lengths. Three membrane-bound folding intermediates of OmpA were discovered in folding studies with dioleoylphosphatidylcholine bilayers. Their formation was monitored by time-resolved distance determinations by fluorescence quenching, and they were structurally distinguished by the relative positions of the five tryptophan residues of OmpA in projection to the membrane normal. Recent studies indicate a chaperone-assisted, highly synchronized mechanism of secondary and tertiary structure formation upon membrane insertion of b-barrel membrane proteins such as OmpA that involves at least three structurally distinct folding intermediates.

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“…These ionizable residues are arranged pairwise but in most cases are too far apart from each other to form salt bridges, thus they constitute potential hydrogen bond donors/acceptors with substrates (7). Crystallographic studies (8) have shown that sugars are involved in van der Waals' contacts with the greasy slide via the hydrophobic face of their glycosyl ring. Multiple H bonds are formed between the sugar hydroxyl groups and the charged residues of the two ionic tracks.…”

mentioning

confidence: 99%

“…Multiple H bonds are formed between the sugar hydroxyl groups and the charged residues of the two ionic tracks. Constant breaking and remaking of these hydrogen bonds has been suggested to allow movement of the substrate through the channel (8,9). The role of the greasy slide in sugar translocation through the channel will be discussed in a future paper.…”

mentioning

confidence: 99%

Sugar Transport through Maltoporin of Escherichia coli

Dumas¹,

Koebnik²,

Winterhalter³

et al. 2000

Journal of Biological Chemistry

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The three-dimensional structure of the maltooligosaccharide specific outer membrane channel LamB of Escherichia coli complexed with sugar molecules revealed a hypothetical transport pathway. Sugars are supposed to slide over a stretch of aromatic residues facilitated by continuous making/breaking of hydrogen bonds between the hydroxyl groups of the sugars and charged amino acids, the "polar tracks." The effect of nine single and three multiple mutations in the polar track residues was investigated by current fluctuations, liposome swelling assays, and in vivo uptake of radiolabeled substrates. Additionally, sugar transport through wild-type LamB was investigated by current fluctuation analysis in water and deuterium. This way the effects on k on and k off could be investigated separately. Analyses of the various mutants revealed a strong effect on the k on values. Because steering to the binding site requires only a few interactions, consequently the loss of even one bond will have a strong effect. Deuterium experiments, which changed the characteristic of all hydrogen bonds, showed a strong effect on k off rates, because at this stage the sugar has numerous interactions with the channel. Furthermore, all the mutations induces a strong decrease of in vivo uptake of sugars. These results clearly demonstrate the importance of the polar track residues on both on and off rates in sugar transport and reveal a strong cooperative effect of hydrogen bond formation.

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Crystal structures of various maltooligosaccharides bound to maltoporin reveal a specific sugar translocation pathway

Abstract: Hydrophobic interactions with the greasy slide guide the sugar into and through the channel constriction. The glucosyl-binding subsites at the channel constriction confer stereospecificity to the channel along with the ability to scavenge substrate at low concentrations.

Cited by 170 publications

References 31 publications

Energy profile of maltooligosaccharide permeation through maltoporin as derived from the structure and from a statistical analysis of saccharide‐protein interactions

Energy profile of maltooligosaccharide permeation through maltoporin as derived from the structure and from a statistical analysis of saccharide‐protein interactions

Membrane protein folding on the example of outer membrane protein A of Escherichia coli

Sugar Transport through Maltoporin of Escherichia coli

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