Ändra sökning
Avgränsa sökresultatet
1 - 9 av 9
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1. Gerttula, S.
    et al.
    Zinkgraf, M.
    Muday, G. K.
    Lewis, D. R.
    Ibatullin, Farid M.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. National Research Center Kurchatov Institute, Russian Federation.
    Brumer, Harry
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. University of British Columbia, Canada.
    Hart, F.
    Mansfield, S. D.
    Filkov, V.
    Groover, A.
    Transcriptional and hormonal regulation of gravitropism of woody stems in populus2015Ingår i: The Plant Cell, ISSN 1040-4651, E-ISSN 1532-298X, Vol. 27, nr 10, s. 2800-2813Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Angiosperm trees reorient their woody stems by asymmetrically producing a specialized xylem tissue, tension wood, which exerts a strong contractile force resulting in negative gravitropism of the stem. Here, we show, in Populus trees, that initial gravity perception and response occurs in specialized cells through sedimentation of starch-filled amyloplasts and relocalization of the auxin transport protein, PIN3. Gibberellic acid treatment stimulates the rate of tension wood formation and gravibending and enhances tissue-specific expression of an auxin-responsive reporter. Gravibending, maturation of contractile fibers, and gibberellic acid (GA) stimulation of tension wood formation are all sensitive to transcript levels of the Class I KNOX homeodomain transcription factor-encoding gene ARBORKNOX2 (ARK2). We generated genome-wide transcriptomes for trees in which gene expression was perturbed by gravistimulation, GA treatment, and modulation of ARK2 expression. These data were employed in computational analyses to model the transcriptional networks underlying wood formation, including identification and dissection of gene coexpression modules associated with wood phenotypes, GA response, and ARK2 binding to genes within modules. We propose a model for gravitropism in the woody stem in which the peripheral location of PIN3-expressing cells relative to the cambium results in auxin transport toward the cambium in the top of the stem, triggering tension wood formation, while transport away from the cambium in the bottom of the stem triggers opposite wood formation.

  • 2.
    Gullfot, Fredrika
    et al.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Ibatullin, Farid
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Sundqvist, Gustav
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Davies, Gideon
    Brumer, Harry
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Functional Characterization of Xyloglucan Glycosynthases from GH7, GH12, and GH16 Scaffolds2009Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, nr 7, s. 1782-1788Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Glycosynthases, hydrolytically inactive mutant glycosidases that catalyze glycosylation reactions using glycosyl fluoride donor substrates, are emerging as useful tools for the synthesis of large, complex polysaccharides [Faijes, M.; Planas, A. Carbohydr. Res. 2007, 342, 1581-1594]. Guided by wild-type xyloglucanase activity, we have produced and characterized new glycosynthases for the synthesis of xyloglucan oligo- and polysaccharides, based on family GH7, GH12, and GH16 scaffolds. The Humicola insolens GH7 glycosynthase, HiCel7B E197S, is capable of synthesizing nongalactosylated, XXXG-based homoxyloglucan up to Mw 60000 [G = Glcβ(1→4); X = Xylα(1→6)Glcβ(1→4); L = Galβ(1→2)Xylα(1→6)Glcβ(1→4)], which is among the largest products so far obtained with glycosynthase technology. Novel glycosynthases based on the GH16 xyloglucan hydrolase from Tropaeolum majus (nasturtium), TmNXG1, are capable of synthesizing XLLG-based xyloglucan oligosaccharides at rates feasible for preparative synthesis, thus providing an essential expansion of product range. Finally, a new glycosynthase based on the recently characterized GH12 xyloglucanase from Bacillus licheniformis, BlXG12 E155A, can perform the condensation of xyloglucosyl fluorides, albeit at poor rates. Altogether, the high catalytic efficiency demonstrated by HiCel7B E197S and the extended product range provided by TmNXG1 E94A are key achievements toward a robust and versatile method for the preparative synthesis of homogeneous xyloglucans with regular substitution patterns not available in nature. Such compounds enable in vitro experimental studies regarding the role of particular structural elements for xyloglucan properties and its interaction with cellulose.

  • 3.
    Ibatullin, Farid M.
    et al.
    KTH, Skolan för bioteknologi (BIO).
    Banasiak, Alicja
    Baumann, Martin J.
    KTH, Skolan för bioteknologi (BIO).
    Greffe, Lionel
    KTH, Skolan för bioteknologi (BIO).
    Takahashi, Junko
    Mellerowicz, Ewa J.
    Brumer, Harry
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    A Real-Time Fluorogenic Assay for the Visualization of Glycoside Hydrolase Activity in Planta2009Ingår i: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 151, nr 4, s. 1741-1750Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There currently exists a diverse array of molecular probes for the in situ localization of polysaccharides, nucleic acids, and proteins in plant cells, including reporter enzyme strategies (e. g. protein-glucuronidase fusions). In contrast, however, there is a paucity of methods for the direct analysis of endogenous glycoside hydrolases and transglycosidases responsible for cell wall remodeling. To exemplify the potential of fluorogenic resorufin glycosides to address this issue, a resorufin beta-glycoside of a xylogluco-oligosaccharide (XXXG-beta-Res) was synthesized as a specific substrate for in planta analysis of XEH activity. The resorufin aglycone is particularly distinguished for high sensitivity in muro assays due to a low pK(a) (5.8) and large extinction coefficient (epsilon 62,000 M-1 cm(-1)), long-wavelength fluorescence (excitation 571 nm/emission 585 nm), and high quantum yield (0.74) of the corresponding anion. In vitro analyses demonstrated that XXXG-beta-Res is hydrolyzed by the archetypal plant XEH, nasturtium (Tropaeolum majus) NXG1, with classical Michaelis-Menten substrate saturation kinetics and a linear dependence on both enzyme concentration and incubation time. Further, XEH activity could be visualized in real time by observing the localized increase in fluorescence in germinating nasturtium seeds and Arabidopsis (Arabidopsis thaliana) inflorescent stems by confocal microscopy. Importantly, this new in situ XEH assay provides an essential complement to the in situ xyloglucan endotransglycosylase assay, thus allowing delineation of the disparate activities encoded by xyloglucan endotransglycosylase/hydrolase genes directly in plant tissues. The observation that XXXG-beta-Res is also hydrolyzed by diverse microbial XEHs indicates that this substrate, and resorufin glycosides in general, may find broad applicability for the analysis of wall restructuring by polysaccharide hydrolases during morphogenesis and plant-microbe interactions.

  • 4.
    Kaewthai, Nomchit
    et al.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Gendre, Delphine
    Eklöf, Jens M.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Ibatullin, Farid M.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Ezcurra, Ines
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Bhalerao, Rishikesh P
    Brumer, Harry
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Group III-A XTH Genes of Arabidopsis Encode Predominant Xyloglucan Endohydrolases That Are Dispensable for Normal Growth2013Ingår i: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 161, nr 1, s. 440-454Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The molecular basis of primary wall extension endures as one of the central enigmas in plant cell morphogenesis. Classical cell wall models suggest that xyloglucan endo-transglycosylase activity is the primary catalyst (together with expansins) of controlled cell wall loosening through the transient cleavage and religation of xyloglucan-cellulose cross links. The genome of Arabidopsis (Arabidopsis thaliana) contains 33 phylogenetically diverse XYLOGLUCAN ENDO-TRANSGLYCOSYLASE/HYDROLASE (XTH) gene products, two of which were predicted to be predominant xyloglucan endohydrolases due to clustering into group III-A. Enzyme kinetic analysis of recombinant AtXTH31 confirmed this prediction and indicated that this enzyme had similar catalytic properties to the nasturtium (Tropaeolum majus) xyloglucanase1 responsible for storage xyloglucan hydrolysis during germination. Global analysis of Genevestigator data indicated that AtXTH31 and the paralogous AtXTH32 were abundantly expressed in expanding tissues. Microscopy analysis, utilizing the resorufin beta-glycoside of the xyloglucan oligosaccharide XXXG as an in situ probe, indicated significant xyloglucan endohydrolase activity in specific regions of both roots and hypocotyls, in good correlation with transcriptomic data. Moreover, this hydrolytic activity was essentially completely eliminated in AtXTH31/AtXTH32 double knockout lines. However, single and double knockout lines, as well as individual overexpressing lines, of AtXTH31 and AtXTH32 did not demonstrate significant growth or developmental phenotypes. These results suggest that although xyloglucan polysaccharide hydrolysis occurs in parallel with primary wall expansion, morphological effects are subtle or may be compensated by other mechanisms. We hypothesize that there is likely to be an interplay between these xyloglucan endohydrolases and recently discovered apoplastic exo-glycosidases in the hydrolytic modification of matrix xyloglucans.

  • 5.
    Larsbrink, Johan
    et al.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Izumi, Atsushi
    Ibatullin, Farid M.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Nakhai, Azadeh
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Gilbert, Harry J.
    Davies, Gideon J.
    Brumer, Harry
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Structural and enzymatic characterization of a glycoside hydrolase family 31 alpha-xylosidase from Cellvibrio japonicus involved in xyloglucan saccharification2011Ingår i: Biochemical Journal, ISSN 0264-6021, E-ISSN 1470-8728, Vol. 436, s. 567-580Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The desire for improved methods of biomass conversion into fuels and feedstocks has re-awakened interest in the enzymology of plant cell wall degradation. The complex polysaccharide xyloglucan is abundant in plant matter, where it may account for up to 20% of the total primary cell wall carbohydrates. Despite this, few studies have focused on xyloglucan saccharification, which requires a consortium of enzymes including endo-xyloglucanases, alpha-xylosidases, beta-galactosidases and alpha-L-fucosidases, among others. In the present paper, we show the characterization of Xy131A, a key alpha-xylosidase in xyloglucan utilization by the model Gram-negative soil saprophyte Cellvibrio japonicus. CjXy131A exhibits high regiospecificity for the hydrolysis of XGOs (xylogluco-oligosaccharides), with a particular preference for longer substrates. Crystallographic structures of both the apo enzyme and the trapped covalent 5-fluoro-beta-xylosyl-enzyme intermediate, together with docking studies with the XXXG heptasaccharide, revealed, for the first time in GH31 (glycoside hydrolase family 31), the importance of PA14 domain insert in the recognition of longer oligosaccharides by extension of the active-site pocket. The observation that CjXy131A was localized to the outer membrane provided support for a biological model of xyloglucan utilization by C. japonicas, in which XGOs generated by the action of a secreted endo-xyloglucanase are ultimately degraded in close proximity to the cell surface. Moreover, the present study diversifies the toolbox of glycosidases for the specific modification and saccharification of cell wall polymers for biotechnological applications.

  • 6.
    Piens, Kathleen
    et al.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Henriksson, Maria
    KTH, Skolan för bioteknologi (BIO).
    Gullfot, Fredrika
    Lopez, Marie
    Fauré, Régis
    Ibatullin, Farid M.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Teeri, Tuula T.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Driguez, Hugues
    Brumer, Harry
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Glycosynthase activity of hybrid aspen xyloglucan endo-transglycosylase PttXET16-34 nucleophile mutants2007Ingår i: Organic and Biomolecular Chemistry, ISSN 1477-0520, Vol. 5, nr 24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Glycosynthases are active-site mutants of glycoside hydrolases that catalyse glycosyl transfer using suitable activated donor substrates without competing product hydrolysis ( S. M. Hancock, M. D. Vaughan and S. G. Withers, Curr. Opin. Chem. Biol., 2006, 10, 509-519). Site-directed mutagenesis of the catalytic nucleophile, Glu-85, of a Populus tremula x tremuloides xyloglucan endo-transglycosylase (PttXET16-34, EC 2.4.1.207) into alanine, glycine, and serine yielded enzymes with glycosynthase activity. Product analysis indicated that PttXET16-34 E85A in particular was able to catalyse regio- and stereospecific homo- and hetero- condensations of alpha-xylogluco-oligosaccharyl fluoride donors XXXG alpha F andXLLG alpha F to produce xyloglucans with regular sidechain substitution patterns. This substrate promiscuity contrasts that of the Humicola insolens Ce17B E197A glycosynthase, which was not able to polymerise the di-galactosylated substrate XLLG alpha F. The production of the PttXET16-34 E85A xyloglucosynthase thus expands the repertoire of glycosynthases to include those capable of synthesising structurally homogenenous xyloglucans

  • 7.
    Spadiut, Oliver
    et al.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Ibatullin, Farid M.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Peart, Jonelle
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Gullfot, Fredrika
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Martinez-Fleites, Carlos
    Ruda, Marcus
    Xu, Chunlin
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Sundqvist, Gustav
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Davies, Gideon J.
    Brumer, Harry
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Building Custom Polysaccharides in Vitro with an Efficient, Broad-Specificity Xyloglucan Glycosynthase and a Fucosyltransferase2011Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, nr 28, s. 10892-10900Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The current drive for applications of biomass-derived compounds, for energy and advanced materials, has led to a resurgence of interest in the manipulation of plant polymers. The xyloglucans, a family of structurally complex plant polysaccharides, have attracted significant interest due to their intrinsic high affinity for cellulose, both in muro and in technical applications. Moreover, current cell wall models are limited by the lack of detailed structure-property relationships of xyloglucans, due to a lack of molecules with well-defined branching patterns. Here, we have developed a new, broad-specificity "xyloglucan glycosynthase", selected from active-site mutants of a bacterial endoxyloglucanase, which catalyzed the synthesis of high molar mass polysaccharides, with complex side-chain structures, from suitable glycosyl fluoride donor substrates. The product range was further extended by combination with an Arabidopsis thaliana alpha(1 -> 2)-fucosyltransferase to achieve the in vitro synthesis of fucosylated xyloglucans typical of dicot primary cell walls. These enzymes thus comprise a toolkit for the controlled enzymatic synthesis of xyloglucans that are otherwise impossible to obtain from native sources. Moreover, this study demonstrates the validity of a chemo-enzymatic approach to polysaccharide synthesis, in which the simplicity and economy of glycosynthase technology is harnessed together with the exquisite specificity of glycosyltransferases to control molecular complexity.

  • 8. Takahashi, Junko
    et al.
    Rudsander, Ulla J.
    KTH, Skolan för kemivetenskap (CHE), Centra, Strategiskt Centrum för Biomimetiska Material, BioMime.
    Hedenstrom, Mattias
    Banasiak, Alicja
    Harholt, Jesper
    Amelot, Nicolas
    Immerzeel, Peter
    Ryden, Peter
    Endo, Satoshi
    Ibatullin, Farid M.
    KTH, Skolan för kemivetenskap (CHE), Centra, Strategiskt Centrum för Biomimetiska Material, BioMime.
    Brumer, Harry
    KTH, Skolan för kemivetenskap (CHE), Centra, Strategiskt Centrum för Biomimetiska Material, BioMime.
    del Campillo, Elena
    Master, Emma R.
    Scheller, Henrik Vibe
    Sundberg, Bjorn
    Teeri, Tuula T.
    KTH, Skolan för kemivetenskap (CHE), Centra, Strategiskt Centrum för Biomimetiska Material, BioMime.
    Mellerowicz, Ewa J.
    KORRIGAN1 and its Aspen Homolog PttCel9A1 Decrease Cellulose Crystallinity in Arabidopsis Stems2009Ingår i: Plant and Cell Physiology, ISSN 0032-0781, E-ISSN 1471-9053, Vol. 50, nr 6, s. 1099-1115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    KORRIGAN1 (KOR1) is a membrane-bound cellulase implicated in cellulose biosynthesis. PttCel9A1 from hybrid aspen (Populus tremula L. tremuloides Michx.) has high sequence similarity to KOR1 and we demonstrate here that it complements kor1-1 mutants, indicating that it is a KOR1 ortholog. We investigated the function of PttCel9A1/KOR1 in Arabidopsis secondary growth using transgenic lines expressing 35S::PttCel9A1 and the KOR1 mutant line irx2-2. The presence of elevated levels of PttCel9A1/KOR1 in secondary walls of 35S::PttCel9A1 lines was confirmed by in muro visualization of cellulase activity. Compared with the wild type, 35S::PttCel9A1 lines had higher trifluoroacetic acid (TFA)-hydrolyzable glucan contents, similar Updegraff cellulose contents and lower cellulose crystallinity indices, as determined by C-13 solid-state nuclear magnetic resonance (NMR) spectroscopy. irx2-2 mutants had wild-type TFA-hydrolyzable glucan contents, but reduced Updegraff cellulose contents and higher than wild-type cellulose crystallinity indices. The data support the hypothesis that PttCel9A1/KOR1 activity is present in cell walls, where it facilitates cellulose biosynthesis in a way that increases the amount of non-crystalline cellulose.

  • 9.
    Takahashi, Junko
    et al.
    KTH, Skolan för bioteknologi (BIO).
    Rudsander, Ulla
    Master, Emma
    Ibatullin, Farid
    Vibe Scheller, Henrik
    Sundberg, Björn
    Teeri, Tuula
    Mellerowicz, Ewa
    Hedenström, Mattias
    Banasiak, Alicja
    Harholt, Jesper
    Amelot, Nicolas
    Ryden, Peter
    Endo, Satoshi
    Brumer, Harry
    del Campillo, Elena
    Expression of aspen homologue of KORRIGAN1, PttCel9A1, affects cellulose crystallinity in secondary growthManuskript (preprint) (Övrigt vetenskapligt)
1 - 9 av 9
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf