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Alphons G. J. Voragen - One of the best experts on this subject based on the ideXlab platform.
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Physicochemical properties of pectins from okra (Abelmoschus esculentus (L.) Moench)
Food Hydrocolloids, 2010Co-Authors: Nipaporn Sengkhamparn, Henk A. Schols, Leonard M.c. Sagis, R.j. De Vries, Tanaboon Sajjaanantakul, Alphons G. J. VoragenAbstract:Abstract Okra pectin obtained by hot buffer extraction (HBSS) consists of an unusual pectic Rhamnogalacturonan I structure in which acetyl groups and alpha galactose residues are substituted on rhamnose residues within the backbone. The okra Chelating agent Soluble Solids (CHSS) pectin consists of slightly different structures since relatively more homogalacturonan is present within the macromolecule and the Rhamnogalacturonan I segments carry slightly longer side chains. The rheological properties of both okra pectins were examined under various conditions in order to understand the unusual slimy behaviour of okra pectins. The viscosity of the okra HBSS pectin was 5–8 times higher than the viscosity of the okra CHSS pectin. The okra HBSS pectin showed an elastic behaviour (G′ > G″) over a wide range of frequencies (10−1–10 Hz), at a strain of 10%, while okra CHSS and saponified okra HBSS/CHSS pectin showed predominantly viscous responses (G′
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Identification of the connecting linkage between homo- or xylogalacturonan and Rhamnogalacturonan type I
Carbohydrate Polymers, 2007Co-Authors: G.j. Coenen, Henk A. Schols, Edwin J. Bakx, René Verhoef, Alphons G. J. VoragenAbstract:Pectin is of interest both as cell wall component and as food additive. The precise chemical structure of pectin remains under debate, although the structural elements of pectin are rather well described. In order to get more insight in the inter linkage between the various structural elements, apple pectin modified hairy regions were degraded by controlled acid hydrolysis. From the degradation products oligomeric fragments were selected which could represent interconnection points, and these oligomers were characterized using LC?MS and NMR approaches. It was shown that the oligomers GalA3Rha1, GalA4Rha2, and GalA5Rha3 consisted out of a homogalacturonan and a Rhamnogalacturonan type I segment connected via a GalAp?-(1 ? 2) Rhap linkage. In addition, a GalA6Rha3Xyl1 oligomer was identified, which consisted out of a xylogalacturonan and a Rhamnogalacturonan type I segment. These oligomers indicated that in apple pectin both homogalacturonan and xylogalacturonan were covalently linked to Rhamnogalacturonan type I. With these new insights, currently used pectin models were refined. Keywords: Homogalacturonan; Xylogalacturonan; Rhamnogalacturonan I; Pectin model; Covalent linkage; Pectin structure
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Structural features of the neutral sugar side chains of apple pectic substances
Carbohydrate Polymers, 2003Co-Authors: J.a. De Vries, Alphons G. J. Voragen, C.h. Den Uijl, Frank M. Rombouts, Walter PilnikAbstract:Abstract The ‘hairy regions’ of apple pectic substances (fragments of the Rhamnogalacturonan chains carrying the neutral sugar side chains) have been subjected to enzymic, acidic and alkaline degradation. The results show that the hairy regions consist of Rhamnogalacturonan fragments carrying arabinogalactans and galacturonan fragments carrying single unit xylose side chains. A separate population of molecules is present consisting of galacturonan main chains and side chains of 1,3/1,6-linked galactans. The structural relations of pectic substances from different plant species are discussed.
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Pectin : the hairy thing : evidence that homogalacturonan is a side chain of Rhamnogalacturonan I
2003Co-Authors: Jean-paul Vincken, Henk A. Schols, Ronald J. F. J. Oomen, Gerrit Beldman, Richard G. F. Visser, Alphons G. J. VoragenAbstract:In vitro degradation studies of pectic polysaccharides with novel fungal pectinases, investigations in which these polymers were treated with dilute acid, and microscopic analysis of extracted pectins have provided clues on how these polysaccharides are linked. Therefore it is believed that pectin is not an extended backbone consisting of homogalacturonan and Rhamnogalacturonan regions, but rather a Rhamnogalacturonan with neutral sugar and homogalacturonan side chains
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Enzymes degrading Rhamnogalacturonan and Xylogalacturonan
2003Co-Authors: Jean-paul Vincken, Alphons G. J. Voragen, Gerrit BeldmanAbstract:This chapter deals with carbohydrases having activity towards the polysaccharides Rhamnogalacturonan and xylogalacturonan
F. Alfred Anderer - One of the best experts on this subject based on the ideXlab platform.
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Enhancement of Human NK and LAK Cytotoxicity against HCMV-Infected Cells by Rhamnogalacturonan: Specificity of Reaction
Viral immunology, 1996Co-Authors: Max Steinmassl, F. Alfred AndererAbstract:ABSTRACT Human peripheral blood mononuclear cells (PBMC) and their subpopulations obtained from healthy donors were used to study improvement of MHC-unrestricted cytotoxic reactions against cells infected with human cytomegalovirus (HCMV) at different multiplicities of infection. Natural killer (NK) and lymphokine-activated killer (LAK) cytotoxicity against HCMV-infected cells was greatly enhanced in the presence of Rhamnogalacturonan (500 ng/ml). The increase of the multiplicity of infection from MOI 0.1 to 1.0 had only a slight effect on cytotoxicity enhancement by Rhamnogalacturonan. The chemical specificity of interaction of Rhamnogalacturonan with effector cells and virus-infected cells was found to be analogous to the interaction with tumor cells, i.e., both types of target cells must express a receptor for Rhamnogalacturonan since Rhamnogalacturonan-mediated enhancement of NK and LAK cytotoxicity against HCMV-infected cells was similarly inhibited by preincubation of CD56+ effector cells with 60% d...
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Enhancement of MHC-unrestricted cytotoxic activity of human CD56^+ CD3^− natural killer (NK) cells and CD3^+ T cells by Rhamnogalacturonan: Target cell specificity and activity against NK-insensitive targets
Journal of Cancer Research and Clinical Oncology, 1994Co-Authors: Thomas Matthias Zollner, Andreas Klein-franke, F. Alfred AndererAbstract:Rhamnogalacturonan-mediated enhancement of MHC-unrestricted cytotoxicity was studied with freshly isolated CD56^+CD3^− natural killer (NK) cells, interleukin-2 (IL-2)-activated CD56^+ lymphokine-activated killer (LAK) cells und IL-2/anti-CD3-activated T cells as effector cells using NK-sensitive and NK-insensitive tumor cells as targets. The Rhamnogalacturonan fractions IM, IP, and IQ were prepared from commercially available extracts of Viscum album . The dose/response relation of IM, IP, and IQ demonstrated the presence of various concentrations of cytotoxicity-enhancing compounds in all three fractions that were identified as Rhamnogalacturonans by degradation studies with poly-α- d -galacturonidase (EC 3.2.1.15) and α-1,6-rhamnosidase (EC 3.2.1.40). Specific cytotoxicity of all three effector cell populations as well as the respective Rhamnogalacturonan-mediated cytotoxicity enhancement was readily inhibited in a dose-dependent manner by 60%-deacetylated mannose pentaacetate. Rhamnogalacturonan-mediated enhancement of cytotoxicity of fresh CD56^+ NK cells was also observed with four of five NK-insensitive tumor cells as targets, indicating that the effector-cell/tumor-cell bridging activity of Rhamnogalacturonans renders NK-insensitive targets susceptible to NK-mediated lysis. Moreover, the Rhamnogalacturonan-mediated cytotoxicity enhancement became even more prominent when lymphokine-activated CD56^+ LAK and CD3^+ T cells were assayed with the NK-insensitive tumor cell targets.
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Enhancement of MHC-unrestricted cytotoxic activity of human CD56^+ CD3^− natural killer (NK) cells and CD3^+ T cells by Rhamnogalacturonan: Target cell specificity and activity against NK-insensitive targets
Journal of Cancer Research and Clinical Oncology, 1994Co-Authors: Thomas Matthias Zollner, Andreas Klein-franke, F. Alfred AndererAbstract:Rhamnogalacturonan-mediated enhancement of MHC-unrestricted cytotoxicity was studied with freshly isolated CD56^+CD3^− natural killer (NK) cells, interleukin-2 (IL-2)-activated CD56^+ lymphokine-activated killer (LAK) cells und IL-2/anti-CD3-activated T cells as effector cells using NK-sensitive and NK-insensitive tumor cells as targets. The Rhamnogalacturonan fractions IM, IP, and IQ were prepared from commercially available extracts of Viscum album . The dose/response relation of IM, IP, and IQ demonstrated the presence of various concentrations of cytotoxicity-enhancing compounds in all three fractions that were identified as Rhamnogalacturonans by degradation studies with poly-α- d -galacturonidase (EC 3.2.1.15) and α-1,6-rhamnosidase (EC 3.2.1.40). Specific cytotoxicity of all three effector cell populations as well as the respective Rhamnogalacturonan-mediated cytotoxicity enhancement was readily inhibited in a dose-dependent manner by 60%-deacetylated mannose pentaacetate. Rhamnogalacturonan-mediated enhancement of cytotoxicity of fresh CD56^+ NK cells was also observed with four of five NK-insensitive tumor cells as targets, indicating that the effector-cell/tumor-cell bridging activity of Rhamnogalacturonans renders NK-insensitive targets susceptible to NK-mediated lysis. Moreover, the Rhamnogalacturonan-mediated cytotoxicity enhancement became even more prominent when lymphokine-activated CD56^+ LAK and CD3^+ T cells were assayed with the NK-insensitive tumor cell targets.
Peter Ulvskov - One of the best experts on this subject based on the ideXlab platform.
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residue specific hydration of primary cell wall potato pectin identified by solid state 13c single pulse mas and cp mas nmr spectroscopy
Biomacromolecules, 2011Co-Authors: Flemming H Larsen, Iben Damager, Peter Ulvskov, Inge Byg, Jerome Diaz, Soren Balling EngelsenAbstract:Hydration of Rhamnogalacturonan-I (RG-I) derived from potato cell wall was analyzed by 13C single-pulse (SP) magic-angle-spinning (MAS) and 13C cross-polarization (CP) MAS nuclear magnetic resonanc...
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Functional characterisation of a putative Rhamnogalacturonan II specific xylosyltransferase.
FEBS letters, 2008Co-Authors: Jack Egelund, Iben Damager, Kirsten Faber, Carl-erik Olsen, Peter Ulvskov, Bent Larsen PetersenAbstract:An Arabidopsis thaliana gene, At1g56550, was expressed in Pichia pastoris and the recombinant protein was shown to catalyse transfer of D-xylose from UDP-alpha-D-xylose onto methyl alpha-L-fucoside. The product formed was shown by 1D and 2D 1H NMR spectroscopy to be Me alpha-D-Xyl-(1,3)-alpha-L-Fuc, which is identical to the proposed target structure in the A-chain of Rhamnogalacturonan II. Chemically synthesized methyl L-fucosides derivatized by methyl groups on either the 2-, 3- or 4 position were tested as acceptor substrates but only methyl 4-O-methyl-alpha-L-fucopyranoside acted as an acceptor, although to a lesser extent than methyl alpha-L-fucoside. At1g56550 is suggested to encode a Rhamnogalacturonan II specific xylosyltransferase.
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Arabidopsis thaliana RGXT1 and RGXT2 Encode Golgi-Localized (1,3)-α-d-Xylosyltransferases Involved in the Synthesis of Pectic Rhamnogalacturonan-II
The Plant cell, 2006Co-Authors: Tadashi Ishii, Jack Egelund, Iben Damager, Carl-erik Olsen, Peter Ulvskov, Bent Larsen Petersen, Naomi Geshi, Mohammed Saddik Motawia, Ahmed Faik, Henrik ClausenAbstract:Two homologous plant-specific Arabidopsis thaliana genes, RGXT1 and RGXT2, belong to a new family of glycosyltransferases (CAZy GT-family-77) and encode cell wall (1,3)-α-d-xylosyltransferases. The deduced amino acid sequences contain single transmembrane domains near the N terminus, indicative of a type II membrane protein structure. Soluble secreted forms of the corresponding proteins expressed in insect cells showed xylosyltransferase activity, transferring d-xylose from UDP-α-d-xylose to l-fucose. The disaccharide product was hydrolyzed by α-xylosidase, whereas no reaction was catalyzed by β-xylosidase. Furthermore, the regio- and stereochemistry of the methyl xylosyl-fucoside was determined by nuclear magnetic resonance to be an α-(1,3) linkage, demonstrating the isolated glycosyltransferases to be (1,3)-α-d-xylosyltransferases. This particular linkage is only known in Rhamnogalacturonan-II, a complex polysaccharide essential to vascular plants, and is conserved across higher plant families. Rhamnogalacturonan-II isolated from both RGXT1 and RGXT2 T-DNA insertional mutants functioned as specific acceptor molecules in the xylosyltransferase assay. Expression of RGXT1- and RGXT2-enhanced green fluorescent protein constructs in Arabidopsis revealed that both fusion proteins were targeted to a Brefeldin A–sensitive compartment and also colocalized with the Golgi marker dye BODIPY TR ceramide, consistent with targeting to the Golgi apparatus. Taken together, these results suggest that RGXT1 and RGXT2 encode Golgi-localized (1,3)-α-d-xylosyltransferases involved in the biosynthesis of pectic Rhamnogalacturonan-II.
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In vitro biosynthesis of 1,4-β-galactan attached to Rhamnogalacturonan I
Planta, 2000Co-Authors: Naomi Geshi, Henrik Vibe Scheller, Peter Ulvskov, Bodil JørgensenAbstract:The biosynthesis of galactan was investigated using microsomal membranes isolated from suspension-cultured cells of potato (Solanum tuberosum L. var. AZY). Incubation of the microsomal membranes in the presence of UDP-[14C]galactose resulted in a radioactive product insoluble in 70% methanol. The product released only [14C]galactose upon acid hydrolysis. Treatment of the product with Aspergillus niger endo-1,4-beta-galactanase released 65-70% of the radioactivity to a 70%-methanol-soluble fraction. To a minor extent, [14C]galactose was also incorporated into proteins, however these galactoproteins were not a substrate for Aspergillus niger endo-1,4-beta-galactanase. Thus, the majority of the 14C-labelled product was 1,4-beta-galactan. Compounds released by the endo-1,4-beta-galactanase treatment were mainly [14C]galactose and [14C]galactobiose, indicating that the synthesized 1,4-beta-galactan was longer than a trimer. In vitro synthesis of 1,4-beta-galactan was most active with 6-d-old cells, which are in the middle of the linear growth phase. The optimal synthesis occurred at pH 6.0 in the presence of 7.5 mM Mn2+. Aspergillus aculeatus rhamnogalacturonase A digested at least 50% of the labelled product to smaller fragments of approx. 14 kDa, suggesting that the synthesized [14C]galactan was attached to the endogenous Rhamnogalacturonan I. When rhamnogalacturonase A digests of the labelled product were subsequently treated with endo-1,4-beta-galactanase, radioactivity was not only found as [14C]galactose or [14C]galactobiose but also as larger fragments. The larger fragments were likely the [14C]galactose or [14C]galactobiose still attached to the Rhamnogalacturonan backbone since treatment with beta-galactosidase together with endo-1,4-beta-galactanase digested all radioactivity to the fraction eluting as [14C]galactose. The data indicate that the majority of the [14C]galactan was attached directly to the rhamnose residues in Rhamnogalacturonan I. Thus, isolated microsomal membranes contain enzyme activities to both initiate and elongate 1,4-beta-galactan sidechains in the endogenous pectic Rhamnogalacturonan I.
Henk A. Schols - One of the best experts on this subject based on the ideXlab platform.
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Physicochemical properties of pectins from okra (Abelmoschus esculentus (L.) Moench)
Food Hydrocolloids, 2010Co-Authors: Nipaporn Sengkhamparn, Henk A. Schols, Leonard M.c. Sagis, R.j. De Vries, Tanaboon Sajjaanantakul, Alphons G. J. VoragenAbstract:Abstract Okra pectin obtained by hot buffer extraction (HBSS) consists of an unusual pectic Rhamnogalacturonan I structure in which acetyl groups and alpha galactose residues are substituted on rhamnose residues within the backbone. The okra Chelating agent Soluble Solids (CHSS) pectin consists of slightly different structures since relatively more homogalacturonan is present within the macromolecule and the Rhamnogalacturonan I segments carry slightly longer side chains. The rheological properties of both okra pectins were examined under various conditions in order to understand the unusual slimy behaviour of okra pectins. The viscosity of the okra HBSS pectin was 5–8 times higher than the viscosity of the okra CHSS pectin. The okra HBSS pectin showed an elastic behaviour (G′ > G″) over a wide range of frequencies (10−1–10 Hz), at a strain of 10%, while okra CHSS and saponified okra HBSS/CHSS pectin showed predominantly viscous responses (G′
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Identification of the connecting linkage between homo- or xylogalacturonan and Rhamnogalacturonan type I
Carbohydrate Polymers, 2007Co-Authors: G.j. Coenen, Henk A. Schols, Edwin J. Bakx, René Verhoef, Alphons G. J. VoragenAbstract:Pectin is of interest both as cell wall component and as food additive. The precise chemical structure of pectin remains under debate, although the structural elements of pectin are rather well described. In order to get more insight in the inter linkage between the various structural elements, apple pectin modified hairy regions were degraded by controlled acid hydrolysis. From the degradation products oligomeric fragments were selected which could represent interconnection points, and these oligomers were characterized using LC?MS and NMR approaches. It was shown that the oligomers GalA3Rha1, GalA4Rha2, and GalA5Rha3 consisted out of a homogalacturonan and a Rhamnogalacturonan type I segment connected via a GalAp?-(1 ? 2) Rhap linkage. In addition, a GalA6Rha3Xyl1 oligomer was identified, which consisted out of a xylogalacturonan and a Rhamnogalacturonan type I segment. These oligomers indicated that in apple pectin both homogalacturonan and xylogalacturonan were covalently linked to Rhamnogalacturonan type I. With these new insights, currently used pectin models were refined. Keywords: Homogalacturonan; Xylogalacturonan; Rhamnogalacturonan I; Pectin model; Covalent linkage; Pectin structure
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Pectin : the hairy thing : evidence that homogalacturonan is a side chain of Rhamnogalacturonan I
2003Co-Authors: Jean-paul Vincken, Henk A. Schols, Ronald J. F. J. Oomen, Gerrit Beldman, Richard G. F. Visser, Alphons G. J. VoragenAbstract:In vitro degradation studies of pectic polysaccharides with novel fungal pectinases, investigations in which these polymers were treated with dilute acid, and microscopic analysis of extracted pectins have provided clues on how these polysaccharides are linked. Therefore it is believed that pectin is not an extended backbone consisting of homogalacturonan and Rhamnogalacturonan regions, but rather a Rhamnogalacturonan with neutral sugar and homogalacturonan side chains
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The CDTA-soluble pectic substances from soybean meal are composed of Rhamnogalacturonan and xylogalacturonan but not homogalacturonan.
Biopolymers, 2001Co-Authors: M. M. H. Huisman, Henk A. Schols, C.t.m. Fransen, Johannis P. Kamerling, Johannes F.g. Vliegenthart, Alphons G. J. VoragenAbstract:Structural characteristics of pectic substances extracted from soybean meal cell walls (water unextractable solids) with a chelating agent-containing buffer (0.05M 1,2-diaminocyclohexane-N,N,N,N-tetraacetic acid (CDTA) and 0.05M NH4-oxalate in 0.05M NaOAc buffer) were studied. The arabinogalactans present as side chains to the Rhamnogalacturonan backbone were largely removed by enzymatic hydrolysis using endo-galactanase, exo-galactanase, endo-arabinanase, and arabinofuranosidase B. The remaining pectic backbone appeared to be resistant to enzymatic degradation by pectolytic enzymes. After partial acid hydrolysis of the isolated pectic backbone, one oligomeric and two polymeric populations were obtained by size-exclusion chromatography. Monosaccharide and linkage analyses, enzymatic degradation, and NMR spectroscopy of these populations showed that the pectic substances in the original extract contain both Rhamnogalacturonan and xylogalacturonan regions, while homogalacturonan is absent.
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Rhamnogalacturonan alpha-D-galactopyranosyluronohydrolase.
Plant physiology, 1998Co-Authors: M. Mutter, Gerrit Beldman, Henk A. Schols, Stuart M. Pitson, Alphons G. J. VoragenAbstract:A new enzyme, Rhamnogalacturonan (RG) α-d-galactopyranosyluronohydrolase (RG-galacturonohydrolase), able to release a galacturonic acid residue from the nonreducing end of RG chains but not from homogalacturonan, was purified from an Aspergillus aculeatus enzyme preparation. RG-galacturonohydrolase acted with inversion of anomeric configuration, initially releasing β-d-galactopyranosyluronic acid. The enzyme cleaved smaller RG substrates with the highest catalytic efficiency. A Michaelis constant of 85 μm and a maximum reaction rate of 160 units mg−1 was found toward a linear RG fragment with a degree of polymerization of 6. RG-galacturonohydrolase had a molecular mass of 66 kD, an isoelectric point of 5.12, a pH optimum of 4.0, and a temperature optimum of 50°C. The enzyme was most stable between pH 3.0 and 6.0 (for 24 h at 40°C) and up to 60°C (for 3 h).
Arun Goyal - One of the best experts on this subject based on the ideXlab platform.
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The multi-ligand binding first family 35 Carbohydrate Binding Module (CBM35) of Clostridium thermocellum targets Rhamnogalacturonan I.
Archives of biochemistry and biophysics, 2018Co-Authors: Arun Dhillon, Kedar Sharma, Vikky Rajulapati, Arun GoyalAbstract:Abstract Carbohydrate Binding Modules (CBMs) targeting cellulose, xylan and mannan have been reported, however, a CBM targeting Rhamnogalacturonan I (RG I) has never been identified. We had studied earlier a Rhamnogalacturonan lyase (CtRGL) from Clostridium thermocellum that was associated with a family 35 CBM, Rgl-CBM35. In this study we show that Rgl-CBM35 displays binding with β- d -glucuronic acid (β-D-GlcpA), Δ4,5-anhydro- d -galactopyranosyluronic acid (Δ4,5-GalpA), Rhamnogalacturonan I, arabinan, galactan, glucuronoxylans and arabinoxylans. Rgl-CBM35 contains a conserved ligand binding site in the loops known for binding β-D-GlcpA and Δ4,5-GalpA moiety of unsaturated RG I and pectic-oligosaccharides. Mutagenesis revealed that Asn118 plays an important role in binding β-D-GlcpA, Δ4,5-GalpA, sugarbeet arabinan and potato galactan at its conserved ligand binding site present in surface exposed loops. EDTA-treated Rgl-CBM35 showed no affinity towards β-D-GlcpA and Δ4,5-GalpA underscoring Ca2+ mediated ligand recognition. Contrastingly, the EDTA-treated Rgl-CBM35 and its mutant N118A displayed affinity for sugarbeet arabinan and potato galactan. The curtailed affinity of Y37A/N118A and R69A/N118A double mutants towards sugarbeet arabinan emphasized the presence of a second ligand binding site. Rgl-CBM35 is the first CBM reported to primarily target RG I and also is the first member of family 35 CBM possessing at least two ligand binding sites.
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STRUCTURE MODELING AND CHARACTERIZATION OF A Rhamnogalacturonan LYASE (CtRGL) FROM Clostridium thermocellum
Journal of Proteins & Proteomics, 2017Co-Authors: Arun Dhillon, Arun GoyalAbstract:The truncated N-terminal catalytic module (CtRGL) of molecular size ~ 64 kDa of cellulosomal Rhamnogalacturonan lyase, (CtRGLf) from Clostridium thermocellum belonging to family 11 polysaccharide lyase(PL11) was structurally characterized. Multiple sequence alignment revealed that CtRGL has conserved active site as well as Ca 2+ binding sites. The secondary structure prediction by PsiPred and Circular Dichroism analysis showed the presence of approximately, 2% α-helix, 30% β-sheet and 65% loops. The structure of CtRGL based on homology modeling showed a β-propeller fold. Structure validation by Ramachandran plot revealed 99.6% residues in allowed region. Comparison of CtRGL structure with that of YesW and YesX proteins from Bacillus subtilis showed conserved catalytic cleft and endo-lytic mode of action. Docking analysis of CtRGL established Arg398, Thr475, Lys476 and Tyr536 as key residues of the active site. Lys476 was predicted to act as a catalytic base and Thr475 as a catalytic acid during â-elimination. This study provides an insight into the structural determinants for mode of action and substrate recognition. Keywords : Rhamnogalacturonan lyase; Rhamnogalacturonan I; Pectin; Polysaccharide lyase; Circular Dichroism; Homology modeling; Docking; Clostridium thermocellum
