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High-resolution structures of a chitinase complexed with natural product cyclopentapeptide inhibitors: Mimicry of carbohydrate substrate

Houston, Douglas R.; Shiomi, Kazuro; Arai, Noriko; Ōmura, Satoshi; Peter, Martin G.; Turberg, Andreas; Synstad, Bjørnar; Eijsink, Vincent G. H.; van Aalten, Daan M. F.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
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Over the past years, family 18 chitinases have been validated as potential targets for the design of drugs against human pathogens that contain or interact with chitin during their normal life cycles. Thus far, only one potent chitinase inhibitor has been described in detail, the pseudotrisaccharide allosamidin. Recently, however, two potent natural-product cyclopentapeptide chitinase inhibitors, argifin and argadin, were reported. Here, we describe high-resolution crystal structures that reveal the details of the interactions of these cyclopeptides with a family 18 chitinase. The structures are examples of complexes of a carbohydrate-processing enzyme with high-affinity peptide-based inhibitors and show in detail how the peptide backbone and side chains mimic the interactions of the enzyme with chitooligosaccharides. Together with enzymological characterization, the structures explain why argadin shows an order of magnitude stronger inhibition than allosamidin, whereas argifin shows weaker inhibition. The peptides bind to the chitinase in remarkably different ways, which may explain the differences in inhibition constants. The two complexes provide a basis for structure-based design of potent chitinase inhibitors, accessible by standard peptide chemistry.

Four Genes of Medicago truncatula Controlling Components of a Nod Factor Transduction Pathway

Catoira, Romy; Galera, Christine; de Billy, Francoise; Penmetsa, R. Varma; Journet, Etienne-Pascal; Maillet, Fabienne; Rosenberg, Charles; Cook, Douglas; Gough, Clare; Dénarié, Jean
Fonte: American Society of Plant Physiologists Publicador: American Society of Plant Physiologists
Tipo: Artigo de Revista Científica
Publicado em /09/2000 EN
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Rhizobium nodulation (Nod) factors are lipo-chitooligosaccharides that act as symbiotic signals, eliciting several key developmental responses in the roots of legume hosts. Using nodulation-defective mutants of Medicago truncatula, we have started to dissect the genetic control of Nod factor transduction. Mutants in four genes (DMI1, DMI2, DMI3, and NSP) were pleiotropically affected in Nod factor responses, indicating that these genes are required for a Nod factor–activated signal transduction pathway that leads to symbiotic responses such as root hair deformations, expressions of nodulin genes, and cortical cell divisions. Mutant analysis also provides evidence that Nod factors have a dual effect on the growth of root hair: inhibition of endogenous (plant) tip growth, and elicitation of a novel tip growth dependent on (bacterial) Nod factors. dmi1, dmi2, and dmi3 mutants are also unable to establish a symbiotic association with endomycorrhizal fungi, indicating that there are at least three common steps to nodulation and endomycorrhization in M. truncatula and providing further evidence for a common signaling pathway between nodulation and mycorrhization.

Genomic Analysis and Initial Characterization of the Chitinolytic System of Microbulbifer degradans Strain 2-40

Howard, Michael B.; Ekborg, Nathan A.; Taylor, Larry E.; Weiner, Ronald M.; Hutcheson, Steven W.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2003 EN
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The marine bacterium Microbulbifer degradans strain 2-40 produces at least 10 enzyme systems for degrading insoluble complex polysaccharides (ICP). The draft sequence of the 2-40 genome allowed a genome-wide analysis of the chitinolytic system of strain 2-40. The chitinolytic system includes three secreted chitin depolymerases (ChiA, ChiB, and ChiC), a secreted chitin-binding protein (CbpA), periplasmic chitooligosaccharide-modifying enzymes, putative sugar transporters, and a cluster of genes encoding cytoplasmic proteins involved in N-acetyl-d-glucosamine (GlcNAc) metabolism. Each chitin depolymerase was detected in culture supernatants of chitin-grown strain 2-40 and was active against chitin and glycol chitin. The chitin depolymerases also had a specific pattern of activity toward the chitin analogs 4-methylumbelliferyl-β-d-N,N′-diacetylchitobioside (MUF-diNAG) and 4-methylumbelliferyl-β-d-N,N′,N"-triacetylchitotrioside (MUF-triNAG). The depolymerases were modular in nature and contained glycosyl hydrolase family 18 domains, chitin-binding domains, and polycystic kidney disease domains. ChiA and ChiB each possessed polyserine linkers of up to 32 consecutive serine residues. In addition, ChiB and CbpA contained glutamic acid-rich domains. At 1...

Lipo-chitooligosaccharide Nodulation Signals from Rhizobium meliloti Induce Their Rapid Degradation by the Host Plant Alfalfa.

Staehelin, C.; Schultze, M.; Kondorosi, E.; Kondorosi, A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1995 EN
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Extracellular enzymes from alfalfa (Medicago sativa L.) involved in the degradation of nodulation (Nod) factors could be distinguished by their different cleavage specificities and were separated by lectin affinity chromatography. A particular glycoprotein was able to release an acylated lipo-disaccharide from all tested Nod factors having an oligosaccharide chain length of four or five residues. Structural modifications of the basic lipo-chitooligosaccharide did not affect the cleavage site and had only weak influence on the cleavage efficiency of Nod factors tested. The acylated lipo-trisaccharide was resistant to degradation. When alfalfa roots were preincubated with Nod factors at nanomolar concentrations, the activity of the dimer-forming enzyme was stimulated up to 6-fold within a few hours. The inducing activity of Nod factors decreased in the order NodRm-IV(C16:2,Ac,S) > NodRm-IV(C16:2,S) and NodRm-V(C16:2,Ac,S) > NodRm-V(C16:2,S) > NodRm-IV(C16:0,S) > NodRm-IV(C16:2). Pretreatment with NodRm-III(C16:2) as well as unmodified chitooligosaccharides did not stimulate the dimer-forming enzyme. Roots preincubated with Rhizobium meliloti showed similar stimulation of the dimer-forming activity. Mutant strains unable to produce Nod factors did not enhance the hydrolytic activity. These results indicate a rapid feedback inactivation of Nod signals after their perception by the host plant alfalfa.

Growth of Hyperthermophilic Archaeon Pyrococcus furiosus on Chitin Involves Two Family 18 Chitinases

Gao, Jun; Bauer, Michael W.; Shockley, Keith R.; Pysz, Marybeth A.; Kelly, Robert M.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2003 EN
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Pyrococcus furiosus was found to grow on chitin, adding this polysacharide to the inventory of carbohydrates utilized by this hyperthermophilic archaeon. Accordingly, two open reading frames (chiA [Pf1234] and chiB [Pf1233]) were identified in the genome of P. furiosus, which encodes chitinases with sequence similarity to proteins from the glycosyl hydrolase family 18 in less-thermophilic organisms. Both enzymes contain multiple domains that consist of at least one binding domain and one catalytic domain. ChiA (ca. 39 kDa) contains a putative signal peptide, as well as a binding domain (ChiABD), that is related to binding domains associated with several previously studied bacterial chitinases. chiB, separated by 37 nucleotides from chiA and in the same orientation, encodes a polypeptide with two different proline-threonine-rich linker regions (6 and 3 kDa) flanking a chitin-binding domain (ChiBBD [11 kDa]), followed by a catalytic domain (ChiBcat [35 kDa]). No apparent signal peptide is encoded within chiB. The two chitinases share little sequence homology to each other, except in the catalytic region, where both have the catalytic glutamic acid residue that is conserved in all family 18 bacterial chitinases. The genes encoding ChiA...

Nod Factor and Elicitors Activate Different Phospholipid Signaling Pathways in Suspension-Cultured Alfalfa Cells1

den Hartog, Martine; Verhoef, Nathalie; Munnik, Teun
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /05/2003 EN
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Lipo-chitooligosaccharides (Nod factors) are produced by symbiotic Rhizobium sp. bacteria to elicit Nod responses on their legume hosts. One of the earliest responses is the formation of phosphatidic acid (PA), a novel second messenger in plant cells. Remarkably, pathogens have also been reported to trigger the formation of PA in nonlegume plants. To investigate how host plants can distinguish between symbionts and pathogens, the effects of Nod factor and elicitors (chitotetraose and xylanase) on the formation of PA were investigated in suspension-cultured alfalfa (Medicago sativa) cells. Theoretically, PA can be synthesized via two signaling pathways, i.e. via phospholipase D (PLD) and via phospholipase C in combination with diacylglycerol (DAG) kinase. Therefore, a strategy involving differential radiolabeling with [32P]orthophosphate was used to determine the contribution of each pathway to PA formation. In support, PLD activity was specifically measured by using the ability of the enzyme to transfer the phosphatidyl group of its substrate to a primary alcohol. In practice, Nod factor, chitotetraose, and xylanase induced the formation of PA and its phosphorylated product DAG pyrophosphate within 2 min of treatment. However, whereas phospholipase C and DAG kinase were activated during treatment with all three different compounds...

Characterization of an Exo-β-d-Glucosaminidase Involved in a Novel Chitinolytic Pathway from the Hyperthermophilic Archaeon Thermococcus kodakaraensis KOD1

Tanaka, Takeshi; Fukui, Toshiaki; Atomi, Haruyuki; Imanaka, Tadayuki
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2003 EN
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We previously clarified that the chitinase from the hyperthermophilic archaeon Thermococcus kodakaraensis KOD1 produces diacetylchitobiose (GlcNAc2) as an end product from chitin. Here we sought to identify enzymes in T. kodakaraensis that were involved in the further degradation of GlcNAc2. Through a search of the T. kodakaraensis genome, one candidate gene identified as a putative β-glycosyl hydrolase was found in the near vicinity of the chitinase gene. The primary structure of the candidate protein was homologous to the β-galactosidases in family 35 of glycosyl hydrolases at the N-terminal region, whereas the central region was homologous to β-galactosidases in family 42. The purified protein from recombinant Escherichia coli clearly showed an exo-β-d-glucosaminidase (GlcNase) activity but not β-galactosidase activity. This GlcNase (GlmATk), a homodimer of 90-kDa subunits, exhibited highest activity toward reduced chitobiose at pH 6.0 and 80°C and specifically cleaved the nonreducing terminal glycosidic bond of chitooligosaccharides. The GlcNase activity was also detected in T. kodakaraensis cells, and the expression of GlmATk was induced by GlcNAc2 and chitin, strongly suggesting that GlmATk is involved in chitin catabolism in T. kodakaraensis. These results suggest that T. kodakaraensis...

Assembly of the Yeast Cell Wall: Crh1p AND Crh2p ACT AS TRANSGLYCOSYLASES IN VIVO AND IN VITRO*S⃞

Cabib, Enrico; Farkas, Vladimir; Kosík, Ondrej; Blanco, Noelia; Arroyo, Javier; McPhie, Peter
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Publicado em 31/10/2008 EN
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The cross-linking of polysaccharides to assemble new cell wall in fungi requires mechanisms by which a preexisting linkage is broken for each new one made, to allow for the absence of free energy sources outside the plasma membrane. Previous work showed that Crh1p and Crh2p, putative transglycosylases, are required for the linkage of chitin to β(1–3)glucose branches of β(1–6)glucan in the cell wall of budding yeast. To explore the linking reaction in vivo and in vitro, we used fluorescent sulforhodamine-linked laminari-oligosaccharides as artificial chitin acceptors. In vivo, fluorescence was detected in bud scars and at a lower level in the cell contour, both being dependent on the CRH genes. The linking reaction was also shown in digitonin-permeabilized cells, with UDP-N-acetylglucosamine as the substrate for nascent chitin production. Both the nucleotide and the Crh proteins were required here. A gas1 mutant that overexpresses Crh1p showed very high fluorescence both in intact and permeabilized cells. In the latter, fluorescence was still incorporated in patches in the absence of UDP-GlcNAc. Isolated cell walls of this strain, when incubated with sulforhodamine-oligosaccharide, also showed Crhp-dependent fluorescence in patches...

Cell Wall Chitosaccharides Are Essential Components and Exposed Patterns of the Phytopathogenic Oomycete Aphanomyces euteiches▿

Badreddine, Ilham; Lafitte, Claude; Heux, Laurent; Skandalis, Nicholas; Spanou, Zacharoula; Martinez, Yves; Esquerré-Tugayé, Marie-Thérèse; Bulone, Vincent; Dumas, Bernard; Bottin, Arnaud
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
EN
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Chitin is an essential component of fungal cell walls, where it forms a crystalline scaffold, and chitooligosaccharides derived from it are signaling molecules recognized by the hosts of pathogenic fungi. Oomycetes are cellulosic fungus-like microorganisms which most often lack chitin in their cell walls. Here we present the first study of the cell wall of the oomycete Aphanomyces euteiches, a major parasite of legume plants. Biochemical analyses demonstrated the presence of ca. 10% N-acetyl-d-glucosamine (GlcNAc) in the cell wall. Further characterization of the GlcNAc-containing material revealed that it corresponds to noncrystalline chitosaccharides associated with glucans, rather than to chitin per se. Two putative chitin synthase (CHS) genes were identified by data mining of an A. euteiches expressed sequence tag collection and Southern blot analysis, and full-length cDNA sequences of both genes were obtained. Phylogeny analysis indicated that oomycete CHS diversification occurred before the divergence of the major oomycete lineages. Remarkably, lectin labeling showed that the Aphanomyces euteiches chitosaccharides are exposed at the cell wall surface, and study of the effect of the CHS inhibitor nikkomycin Z demonstrated that they are involved in cell wall function. These data open new perspectives for the development of antioomycete drugs and further studies of the molecular mechanisms involved in the recognition of pathogenic oomycetes by the host plants.

Streptococcus mutans SMU.623c Codes for a Functional, Metal-Dependent Polysaccharide Deacetylase That Modulates Interactions with Salivary Agglutinin▿ †

Deng, Dong Mei; Urch, Jonathan E.; ten Cate, Jacob M.; Rao, Vincenzo A.; van Aalten, Daan M. F.; Crielaard, Wim
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
EN
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The genome sequence of the oral pathogen Streptococcus mutans predicts the presence of two putative polysaccharide deacetylases. The first, designated PgdA in this paper, shows homology to the catalytic domains of peptidoglycan deacetylases from Streptococcus pneumoniae and Listeria monocytogenes, which are both thought to be involved in the bacterial defense mechanism against human mucosal lysozyme and are part of the CAZY family 4 carbohydrate esterases. S. mutans cells in which the pgdA gene was deleted displayed a different colony texture and a slightly increased cell surface hydrophobicity and yet did not become hypersensitive to lysozyme as shown previously for S. pneumoniae. To understand this apparent lack of activity, the high-resolution X-ray structure of S. mutans PgdA was determined; it showed the typical carbohydrate esterase 4 fold, with metal bound in a His-His-Asp triad. Analysis of the protein surface showed that an extended groove lined with aromatic residues is orientated toward the active-site residues. The protein exhibited metal-dependent de-N-acetylase activity toward a hexamer of N-acetylglucosamine. No activity was observed toward shorter chitooligosaccharides or a synthetic peptidoglycan tetrasaccharide. In agreement with the lysozyme data this would suggest that S. mutans PgdA does not act on peptidoglycan but on an as-yet-unidentified polysaccharide within the bacterial cell surface. Strikingly...

Chitin signaling and plant disease resistance

Wan, Jinrong; Zhang, Xue-Cheng; Stacey, Gary
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
Publicado em /10/2008 EN
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Chitin, a polymer of N-acetyl-D-glucosamine, is a component of the fungal cell wall and is not found in plants. Plant cells are equipped with chitin degrading enzymes to digest fungal cell walls and are capable of perceiving chitin fragments (chitooligosaccharides) released from fungal cell walls during fungal infection. Chitin recognition results in the activation of defense signaling pathways. Although chitin is a well recognized pathogen-associated molecular pattern (PAMP), little is known about the molecular mechanism of chitin signaling. Recent studies identified a number of critical components in the chitin-elicited signaling pathway including a potential receptor, MAPK cascade and transcription factor network. Interestingly, the chitin signaling pathway overlaps with the phytobacterial flagellin-and EF-Tu-elicited signaling pathways, suggesting that plant cells may perceive different PAMPs from various pathogens via specialized receptors and then utilize a conserved, common downstream pathway to mediate disease resistance. Given the fact that fungal pathogens are major problems in many agricultural systems, research on chitin signaling could have significance to sustainable agriculture and biofuel and biomaterial production.

Prebiotic oligosaccharides change the concentrations of short-chain fatty acids and the microbial population of mouse bowel*

Pan, Xiao-dong; Chen, Fen-qin; Wu, Tian-xing; Tang, Hong-gang; Zhao, Zhan-yu
Fonte: Zhejiang University Press Publicador: Zhejiang University Press
Tipo: Artigo de Revista Científica
Publicado em /04/2009 EN
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The purpose of this study was to clarify effects of selected oligosaccharides on concentrations of cecal short-chain fatty acids (SCFAs), total large bowel wet weight and wall weight, and cecal microbiota levels in mice. Mice were respectively given gavage of selected fructooligosaccharides (FOS), galactooligosaccharides (GOS), mannanoligosaccharides (MOS), and chitooligosaccharides (COS) [1000 mg/(kg body weight·d)]. Control group was given physiological saline solution. After 14 d treatment, SCFAs and lactate in mice cecum were significantly increased (P<0.05) by intake of oligosaccharides, especially FOS and GOS. Thus, providing these oligosaccharides as ingredients in nutritional formulas may benefit the gastrointestinal tract.

Caught at its own game: regulatory small RNA inactivated by an inducible transcript mimicking its target

Figueroa-Bossi, Nara; Valentini, Martina; Malleret, Laurette; Bossi, Lionello
Fonte: Cold Spring Harbor Laboratory Press Publicador: Cold Spring Harbor Laboratory Press
Tipo: Artigo de Revista Científica
Publicado em 01/09/2009 EN
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A relevant, yet little recognized feature of antisense regulation is the possibility of switching roles between regulatory and regulated RNAs. Here we show that induction of a Salmonella gene relies on the conversion of a small RNA from effector to regulatory target. The chiP gene (formerly ybfM), identified and characterized in the present study, encodes a conserved enterobacterial chitoporin required for uptake of chitin-derived oligosaccharides. In the absence of inducer, chiP is kept silent by the action of a constitutively made small RNA, ChiX (formerly SroB, RybC), which pairs with a sequence at the 5′ end of chiP mRNA. Silencing is relieved in the presence of chitooligosaccharides due to the accumulation of an RNA that pairs with ChiX and promotes its degradation. Anti-ChiX RNA originates from an intercistronic region of the chb operon, which comprises genes for chitooligosaccharide metabolism and whose transcription is activated in the presence of these sugars. We present evidence suggesting that the chb RNA destabilizes ChiX sRNA by invading the stem of its transcription terminator hairpin. Overall, our findings blur the distinction between effector and target in sRNA regulation, raising the possibility that some of the currently defined targets could actually be inhibitors of sRNA function.

Role for Chitin and Chitooligomers in the Capsular Architecture of Cryptococcus neoformans▿

Fonseca, Fernanda L.; Nimrichter, Leonardo; Cordero, Radames J. B.; Frases, Susana; Rodrigues, Jessica; Goldman, David L.; Andruszkiewicz, Ryszard; Milewski, Sławomir; Travassos, Luiz R.; Casadevall, Arturo; Rodrigues, Marcio L.
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
EN
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Molecules composed of β-1,4-linked N-acetylglucosamine (GlcNAc) and deacetylated glucosamine units play key roles as surface constituents of the human pathogenic fungus Cryptococcus neoformans. GlcNAc is the monomeric unit of chitin and chitooligomers, which participate in the connection of capsular polysaccharides to the cryptococcal cell wall. In the present study, we evaluated the role of GlcNAc-containing structures in the assembly of the cryptococcal capsule. The in vivo expression of chitooligomers in C. neoformans varied depending on the infected tissue, as inferred from the differential reactivity of yeast forms to the wheat germ agglutinin (WGA) in infected brain and lungs of rats. Chromatographic and dynamic light-scattering analyses demonstrated that glucuronoxylomannan (GXM), the major cryptococcal capsular component, interacts with chitin and chitooligomers. When added to C. neoformans cultures, chitooligomers formed soluble complexes with GXM and interfered in capsular assembly, as manifested by aberrant capsules with defective connections with the cell wall and no reactivity with a monoclonal antibody to GXM. Cultivation of C. neoformans in the presence of an inhibitor of glucosamine 6-phosphate synthase resulted in altered expression of cell wall chitin. These cells formed capsules that were loosely connected to the cryptococcal wall and contained fibers with decreased diameters and altered monosaccharide composition. These results contribute to our understanding of the role played by chitin and chitooligosaccharides on the cryptococcal capsular structure...

Substrate binding modes and anomer selectivity of chitinase A from Vibrio harveyi

Suginta, Wipa; Pantoom, Supansa; Prinz, Heino
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
EN
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High-performance liquid chromatography mass spectrometry (HPLC MS) was employed to assess the binding behaviors of various substrates to Vibrio harveyi chitinase A. Quantitative analysis revealed that hexaNAG preferred subsites −2 to +2 over subsites −3 to +2 and pentaNAG only required subsites −2 to +2, while subsites −4 to +2 were not used at all by both substrates. The results suggested that binding of the chitooligosaccharides to the enzyme essentially occurred in compulsory fashion. The symmetrical binding mode (−2 to +2) was favored presumably to allow the natural form of sugars to be utilized effectively. Crystalline α chitin was initially hydrolyzed into a diverse ensemble of chitin oligomers, providing a clear sign of random attacks that took place within chitin chains. However, the progressive degradation was shown to occur in greater extent at later time to complete hydrolysis. The effect of the reducing-end residues were also investigated by means of HPLC MS. Substitutions of Trp275 to Gly and Trp397 to Phe significantly shifted the anomer selectivity of the enzyme toward β substrates. The Trp275 mutation modulated the kinetic property of the enzyme by decreasing the catalytic constant (kcat) and the substrate specificity (kcat/Km) toward all substrates by five- to tenfold. In contrast...

Structural basis for chitotetraose-coordination by CGL3, a novel galectin-related protein from Coprinopsis cinerea

Wälti, Martin Andreas; Walser, Piers Jamie; Thore, Stéphane; Grünler, Anke; Bednar, Michaela; Künzler, Markus; Aebi, Markus
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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Recent advances in genome sequencing efforts have revealed an abundance of novel putative lectins. Amongst these, many galectin-related proteins have been found in all corners of the eukaryotic superkingdom, characterized by many conserved residues but intriguingly lacking critical amino acids. Here we present a structural and biochemical analysis of one representative, the galectin-related lectin CGL3 found in the inky cap mushroom Coprinopsis cinerea. This protein contains all but one conserved residues known to be involved in β-galactoside binding in galectins. A Trp residue strictly conserved among galectins is changed to an Arg in CGL3 (R81). Accordingly, the galectin-related protein is not able to bind lactose. Screening of a glycan array revealed that CGL3 displays preference for oligomers of β1-4 linked N-acetyl-glucosamines (chitooligosaccharides) and GalNAcβ1-4GlcNAc (LacdiNAc). Carbohydrate-binding affinity of this novel lectin was quantified using isothermal titration calorimetry and its mode of chitooligosaccharide coordination, not involving any aromatic amino acid residues, was studied by x-ray crystallography. The structural information was used to alter the carbohydrate-binding specificity and substrate affinity of CGL3. The importance of residue R81 in determining the carbohydrate-binding specificity was demonstrated by replacing this Arg by a Trp residue (R81W). This single amino acid change led to a lectin that failed to bind chitooligosaccarides but gained lactose-binding. Our results demonstrate that...

Regulation of Microbe-Associated Molecular Pattern-Induced Hypersensitive Cell Death, Phytoalexin Production, and Defense Gene Expression by Calcineurin B-Like Protein-Interacting Protein Kinases, OsCIPK14/15, in Rice Cultured Cells1[W][OA]

Kurusu, Takamitsu; Hamada, Jumpei; Nokajima, Hiroshi; Kitagawa, Youichiro; Kiyoduka, Masahiro; Takahashi, Akira; Hanamata, Shigeru; Ohno, Ryoko; Hayashi, Teruyuki; Okada, Kazunori; Koga, Jinichiro; Hirochika, Hirohiko; Yamane, Hisakazu; Kuchitsu, Kazuyuki
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
EN
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Although cytosolic free Ca2+ mobilization induced by microbe/pathogen-associated molecular patterns is postulated to play a pivotal role in innate immunity in plants, the molecular links between Ca2+ and downstream defense responses still remain largely unknown. Calcineurin B-like proteins (CBLs) act as Ca2+ sensors to activate specific protein kinases, CBL-interacting protein kinases (CIPKs). We here identified two CIPKs, OsCIPK14 and OsCIPK15, rapidly induced by microbe-associated molecular patterns, including chitooligosaccharides and xylanase (Trichoderma viride/ethylene-inducing xylanase [TvX/EIX]), in rice (Oryza sativa). Although they are located on different chromosomes, they have over 95% nucleotide sequence identity, including the surrounding genomic region, suggesting that they are duplicated genes. OsCIPK14/15 interacted with several OsCBLs through the FISL/NAF motif in yeast cells and showed the strongest interaction with OsCBL4. The recombinant OsCIPK14/15 proteins showed Mn2+-dependent protein kinase activity, which was enhanced both by deletion of their FISL/NAF motifs and by combination with OsCBL4. OsCIPK14/15-RNAi transgenic cell lines showed reduced sensitivity to TvX/EIX for the induction of a wide range of defense responses...

Chitosan Modification and Pharmaceutical/Biomedical Applications

Zhang, Jiali; Xia, Wenshui; Liu, Ping; Cheng, Qinyuan; Tahirou, Talba; Gu, Wenxiu; Li, Bo
Fonte: Molecular Diversity Preservation International Publicador: Molecular Diversity Preservation International
Tipo: Artigo de Revista Científica
Publicado em 25/06/2010 EN
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Chitosan has received much attention as a functional biopolymer for diverse applications, especially in pharmaceutics and medicine. Our recent efforts focused on the chemical and biological modification of chitosan in order to increase its solubility in aqueous solutions and absorbability in the in vivo system, thus for a better use of chitosan. This review summarizes chitosan modification and its pharmaceutical/biomedical applications based on our achievements as well as the domestic and overseas developments: (1) enzymatic preparation of low molecular weight chitosans/chitooligosaccharides with their hypocholesterolemic and immuno-modulating effects; (2) the effects of chitin, chitosan and their derivatives on blood hemostasis; and (3) synthesis of a non-toxic ion ligand—D-Glucosaminic acid from Oxidation of D-Glucosamine for cancer and diabetes therapy.

Potential Anti-HIV Agents from Marine Resources: An Overview

Vo, Thanh-Sang; Kim, Se-Kwon
Fonte: Molecular Diversity Preservation International Publicador: Molecular Diversity Preservation International
Tipo: Artigo de Revista Científica
Publicado em 29/11/2010 EN
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Human immunodeficiency virus (HIV) infection causes acquired immune deficiency syndrome (AIDS) and is a global public health issue. Anti-HIV therapy involving chemical drugs has improved the life quality of HIV/AIDS patients. However, emergence of HIV drug resistance, side effects and the necessity for long-term anti-HIV treatment are the main reasons for failure of anti-HIV therapy. Therefore, it is essential to isolate novel anti-HIV therapeutics from natural resources. Recently, a great deal of interest has been expressed regarding marine-derived anti-HIV agents such as phlorotannins, sulfated chitooligosaccharides, sulfated polysaccharides, lectins and bioactive peptides. This contribution presents an overview of anti-HIV therapeutics derived from marine resources and their potential application in HIV therapy.

Applications of Chitin and Its Derivatives in Biological Medicine

Park, Bae Keun; Kim, Moon-Moo
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 15/12/2010 EN
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Chitin and its derivatives—as a potential resource as well as multiple functional substrates—have generated attractive interest in various fields such as biomedical, pharmaceutical, food and environmental industries, since the first isolation of chitin in 1811. Moreover, chitosan and its chitooligosaccharides (COS) are degraded products of chitin through enzymatic and acidic hydrolysis processes; and COS, in particular, is well suited for potential biological application, due to the biocompatibility and nontoxic nature of chitosan. In this review, we investigate the current bioactivities of chitin derivatives, which are all correlated with their biomedical properties. Several new and cutting edge insights here may provide a molecular basis for the mechanism of chitin, and hence may aid its use for medical and pharmaceutical applications.