1.
Aspholm-Hurtig, Marina, et al.
(författare)
Functional adaptation of BabA, the H. pylori ABO blood group antigen binding adhesin.
2004
Ingår i: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 305:5683, s. 519-22
Tidskriftsartikel (refereegranskat) abstract
Adherence by Helicobacter pylori increases the risk of gastric disease. Here, we report that more than 95% of strains that bind fucosylated blood group antigen bind A, B, and O antigens (generalists), whereas 60% of adherent South American Amerindian strains bind blood group O antigens best (specialists). This specialization coincides with the unique predominance of blood group O in these Amerindians. Strains differed about 1500-fold in binding affinities, and diversifying selection was evident in babA sequences. We propose that cycles of selection for increased and decreased bacterial adherence contribute to babA diversity and that these cycles have led to gradual replacement of generalist binding by specialist binding in blood group O-dominant human populations.
2.
Wahlgren, Weixiao Yuan, 1970, et al.
(författare)
Substrate-bound outward-open structure of a Na+-coupled sialic acid symporter reveals a new Na+ site.
2018
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1
Tidskriftsartikel (refereegranskat) abstract
Many pathogenic bacteria utilise sialic acids as an energy source or use them as an external coating to evade immune detection. As such, bacteria that colonise sialylated environments deploy specific transporters to mediate import of scavenged sialic acids. Here, we report a substrate-bound 1.95Å resolution structure and subsequent characterisation of SiaT, a sialic acid transporter from Proteus mirabilis. SiaT is a secondary active transporter of the sodium solute symporter (SSS) family, which use Na+ gradients to drive the uptake of extracellular substrates. SiaT adopts the LeuT-fold and is in an outward-open conformation in complex with the sialic acid N-acetylneuraminic acid and two Na+ ions. One Na+ binds to the conserved Na2 site, while the second Na+ binds to a new position, termed Na3, which is conserved in many SSS family members. Functional and molecular dynamics studies validate the substrate-binding site and demonstrate that both Na+ sites regulate N-acetylneuraminic acid transport.
3.
4.
Bergh, Anders, et al.
(författare)
Cobalt-mediated solid phase synthesis of 3-O-alkynylbenzyl galactosides and their evaluation as galectin inhibitors
2006
Ingår i: Tetrahedron. - : Elsevier BV. - 0040-4020. ; 62:35, s. 8309-8317
Tidskriftsartikel (refereegranskat) abstract
Methyl beta-D-galactoside was converted to the corresponding 3,4-O-stannylene acetal, which was selectively benzylated with 3-iodobenzyl bromide and coupled to a polymer-bound propargylic ether via a Sonogashira reaction. The polymer-bound carbohydrate substrate was cleaved from the resin with different carbon nucleophiles in a cobalt-mediated Nicholas reaction. The product 3-O-alkynylbenzyl galactosides were screened towards galectin-1, -3, -7, -8N and -9N in a competitive fluorescence polarisation assay. Particularly potent inhibitors were identified against galectin-7 with affinity enhancements up to one order of magnitude due to the 3-O-alkynylbenzyl moiety. (c) 2006 Elsevier Ltd. All rights reserved.
5.
Bum-Erdene, Khuchtumur, et al.
(författare)
Investigation into the Feasibility of Thioditaloside as a Novel Scaffold for Galectin-3-Specific Inhibitors
2013
Ingår i: ChemBioChem. - : Wiley. - 1439-4227. ; 14:11, s. 1331-1342
Tidskriftsartikel (refereegranskat) abstract
Galectin-3 is extensively involved in metabolic and disease processes, such as cancer metastasis, thus giving impetus for the design of specific inhibitors targeting this -galactose-binding protein. Thiodigalactoside (TDG) presents a scaffold for construction of galectin inhibitors, and its inhibition of galectin-1 has already demonstrated beneficial effects as an adjuvant with vaccine immunotherapy, thereby improving the survival outcome of tumour-challenged mice. A novel approachreplacing galactose with its C2 epimer, taloseoffers an alternative framework, as extensions at C2 permit exploitation of a galectin-3-specific binding groove, thereby facilitating the design of selective inhibitors. We report the synthesis of thioditaloside (TDT) and crystal structures of the galectin-3 carbohydrate recognition domain in complexes with TDT and TDG. The different abilities of galactose and talose to anchor to the protein correlate with molecular dynamics studies, likely explaining the relative disaccharide binding affinities. The feasibility of a TDT scaffold to enable access to a particular galectin-3 binding groove and the need for modifications to optimise such a scaffold for use in the design of potent and selective inhibitors are assessed.
6.
Cumpstey, Ian, et al.
(författare)
Double Affinity Amplification of Galectin-Ligand Interactions through Arginine-Arene Interactions: Synthetic, Thermodynamic, and Computational Studies with Aromatic Diamido-Thiodigalactosides.
2008
Ingår i: Chemistry: A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 14:14, s. 4233-4245
Tidskriftsartikel (refereegranskat) abstract
A series of aromatic mono- or diamido-thiodigalactoside derivatives were synthesized and studied as ligands for galectin-1, -3, -7, -8N terminal domain, and -9N terminal domain. The affinity determination in vitro with competitive fluorescence-polarization experiments and thermodynamic analysis by isothermal microcalorimetry provided a coherent picture of structural requirements for arginine-arene interactions in galectin-ligand binding. Computational studies were employed to explain binding preferences for the different galectins. Galectin-3 formed two almost ideal arene-arginine stacking interactions according to computer modeling and also had the highest affinity for the diamido-thiodigalactosides (K(d) below 50 nM). Site-directed mutagenesis of galectin-3 arginines involved in binding corroborated the importance of their interaction with the aromatic diamido-thiodigalactosides. Furthermore, the arginine mutants revealed distinct differences between free, flexible, and solvent-exposed arginine side chains and tightly ion-paired arginine side chains in interactions with aromatic systems.
7.
Cumpstey, Ian, et al.
(författare)
Studies of arginine-arene interactions through synthesis and evaluation of a series of galectin-binding aromatic lactose esters
2007
Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 8:12, s. 1389-1398
Tidskriftsartikel (refereegranskat) abstract
Aromatic lactose 2-O-esters were synthesized and used to probe arene-arginine interactions with the galectin family of proteins. They were found to be low mu m inhibitors of galectin-1, -3, and -9N-terminal domain and moderate inhibitors of galectin-7, but not inhibitors of galectin-8N-terminal, which locks an arginine residue close to the critical, esterified lactose 2-O-position. Molecular modeling of galectins in complex with aromatic lactose 2-O-esters, as well as binding studies with a galectin-3 R186S mutant, confirmed that the inhibitory efficiency of the lactose 2-O-esters was due to the formation of strong interactions between the aromatic ester moieties and the arginine guanidinium groups of galectin-1 and -3. An important common feature shared by galectin-1 and -3 was that the arginines formed in-plane ion pairs with two side-chain carboxylates, which resulted in extended planar pi-electron surfaces that did not require solvation by water; these surfaces were ideal for stocking with aromatic moieties of the ligands. The results provide a basis for the design of lectin inhibitors and drugs that exploit interactions with arginine side-chains via aromatic moieties, which are involved in intramolecular protein salt bridges.
8.
Diehl, Carl, et al.
(författare)
Protein Flexibility and Conformational Entropy in Ligand Design Targeting the Carbohydrate Recognition Domain of Galectin-3.
2010
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 132, s. 14577-14589
Tidskriftsartikel (refereegranskat) abstract
Rational drug design is predicated on knowledge of the three-dimensional structure of the protein-ligand complex and the thermodynamics of ligand binding. Despite the fundamental importance of both enthalpy and entropy in driving ligand binding, the role of conformational entropy is rarely addressed in drug design. In this work, we have probed the conformational entropy and its relative contribution to the free energy of ligand binding to the carbohydrate recognition domain of galectin-3. Using a combination of NMR spectroscopy, isothermal titration calorimetry, and X-ray crystallography, we characterized the binding of three ligands with dissociation constants ranging over 2 orders of magnitude. (15)N and (2)H spin relaxation measurements showed that the protein backbone and side chains respond to ligand binding by increased conformational fluctuations, on average, that differ among the three ligand-bound states. Variability in the response to ligand binding is prominent in the hydrophobic core, where a distal cluster of methyl groups becomes more rigid, whereas methyl groups closer to the binding site become more flexible. The results reveal an intricate interplay between structure and conformational fluctuations in the different complexes that fine-tunes the affinity. The estimated change in conformational entropy is comparable in magnitude to the binding enthalpy, demonstrating that it contributes favorably and significantly to ligand binding. We speculate that the relatively weak inherent protein-carbohydrate interactions and limited hydrophobic effect associated with oligosaccharide binding might have exerted evolutionary pressure on carbohydrate-binding proteins to increase the affinity by means of conformational entropy.
9.
Gouin, Sebastien G., et al.
(författare)
Multimeric Lactoside "Click Clusters" as Tools to Investigate the Effect of Linker Length in Specific Interactions with Peanut Lectin, Galectin-1, and-3
2010
Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 11:10, s. 1430-1442
Tidskriftsartikel (refereegranskat) abstract
Multimeric lactosides based on carbohydrate scaffolds with valencies ranging from 1 to 4 and different linker lengths were synthesized by a copper-catalyzed azide-alkyne cycloaddition (CuAAC). The binding affinities and crosslinking abilities of the new "click clusters" toward biologically relevant galectins (gal-1, gal-3) and peanut lectin were evaluated by fluorescent polarization assay (FPA) and enzyme-linked lectin assay (ELLA), respectively. FPA indicated that the binding affinities of the synthetic multilactosides towards the galectins increased proportionally with their lactosyl content, without significant differences due to the spacer length. ELLA evidenced a modest cluster effect for the multivalent conjugates, with a relative potency per lactoside ranging from 2.1 to 3.2. Nearly identical binding affinities were recorded for derivatives differing in the length of the linkers, in agreement with the FPA data. These results demonstrate that this parameter does not significantly influence the recognition process when interactions occur at a single lectin site. Molecular dynamics revealed that glycoconjugates adopt a pseudoglobular structure with a random localization of the lactoside residues. These spatial distributions were observed irrespective of the linker length; this explains the virtually equal affinities recorded by ELLA. In contrast, two-site "sandwich" ELLA clearly revealed that multivalent derivatives bearing the longest spacers were more efficient for crosslinking lectins. Intrinsic affinities, devoid of aggregation effects, and crosslinking capabilities are, therefore, not directly related phenomena that must be taking into consideration in neoglycoconjugate design for specific applications.
10.
Leffler, Hakon, et al.
(författare)
Low-Molecular Weight Inhibitors of Galectins
2012
Ingår i: Galectins and Disease Implications for Targeted Therapeutics. - Washington, DC : American Chemical Society. - 0097-6156. ; 1115, s. 47-59
Konferensbidrag (refereegranskat) abstract
The galectins are known to be able to recognize and cross-link beta-D-galactopyranoside-containing glycoconjugates as a result of presenting multiple binding sites. This review summarizes efforts in our group for the last ten years towards low-molecular weight chemically modified carbohydrate derivatives. In addition to providing an avenue for improved affinity and galectin-selectivity, we have focused on the chemical synthesis of low-molecular weight inhibitors, since synthetic derivatives offer opportunities to design more "drug-like" in order to circumvent drawbacks typically associated with natural oligosaccharides and fragments, such as low affinity (high mu M to mM for galectins), limited chemical and metabolic stability, and high polarity leading to low bioavailability and rapid clearance. The examples described in the review provide evidence that it is possible to improve both affinity and selectivity of low-molecular weight compounds for galectins by chemically modifying galactose (and other monosaccharides) with non-carbohydrate structural elements targeting ligand sub-sites flanking the core galactose-binding sub-site C. Indeed, inhibitors have been made that possess both low-nM affinities for galectins and that show potent in vivo efficacy. Hence, promising low-molecular weight galectin-targeting lead structures have been identified, although it remains to investigate and optimize ADME and toxicology aspects of these compounds in order to fully reach the status of identifying clinical candidates.
