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  • 1
    Electronic Resource
    Electronic Resource
    THE CELLULOSOMES: Multienzyme Machines for Degradation of Plant Cell Wall Polysaccharides (2004)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Microbiology 58 (2004), S. 521-554 
    Details
    ISSN: 0066-4227
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: The discrete multicomponent, multienzyme cellulosome complex of anaerobic cellulolytic bacteria provides enhanced synergistic activity among the different resident enzymes to efficiently hydrolyze intractable cellulosic and hemicellulosic substrates of the plant cell wall. A pivotal noncatalytic subunit called scaffoldin secures the various enzymatic subunits into the complex via the cohesin-dockerin interaction. The specificity characteristics and tenacious binding between the scaffoldin-based cohesin modules and the enzyme-borne dockerin domains dictate the supramolecular architecture of the cellulosome. The diversity in cellulosome architecture among the known cellulosome-producing bacteria is manifest in the arrangement of their genes in either multiple-scaffoldin or enzyme-linked clusters on the genome. The recently described three-dimensional crystal structure of the cohesin-dockerin heterodimer sheds light on the critical amino acids that contribute to this high-affinity protein-protein interaction. In addition, new information regarding the regulation of cellulosome-related genes, budding genetic tools, and emerging genomics of cellulosome-producing bacteria promises new insight into the assembly and consequences of the multienzyme complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.micro.57.030502.091022
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  • 2
    Electronic Resource
    Electronic Resource
    Crystallization and preliminary X-ray analysis of an intracellular xylanase from Bacillus stearothermophilus T-6 (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 181-184 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Xylanases (1,4-β-D-xylan xylanhydrolases; E.C. 3.2.1.8) hydrolyze the 1,4-β-D-xylopyranosyl linkage of xylans. The structural characterization of xylanase active sites is of great interest, since it can lead to a better understanding of their catalytic mechanism and contribute significant knowledge to the rational design of specific oligosaccharide-binding sites via protein engineering. An intracellular xylanase gene (xynA2) from Bacillus stearothermophilus T-6 has recently been cloned and sequenced. The xynA2 gene encodes for an intracellular enzyme (IXT6) of 331 amino acids, with a calculated molecular weight of 38 639 Da and a pI of 5.72. Based on sequence homology, the enzyme belongs to family 10 of the glycosyl hydrolases. The xynA2 gene product (IXT6) was overproduced in Escherichia coli and purified to homogeneity. Crystallographic studies of IXT6 were initiated in order to study the specificity and mechanism of catalysis of this unique xylanase, as well as to provide a structural basis for rational introduction of enhanced thermostability by site-specific mutagenesis. The M1 crystal form was found to be the most suitable for detailed crystal structure analysis. These crystals belong to a C-centered monoclinic crystal system (space group C2) with unit-cell parameters a = 170.6, b = 82.5, c = 80.0 Å, β = 91.43°. They are mechanically strong, are fairly stable in the X-ray beam and diffract X-rays to better than 2.5 Å resolution. A full 2.9 Å resolution diffraction data set (97.9% completeness, Rmerge = 8.4%) has recently been collected from one crystal at room temperature using X-ray synchrotron radiation (λ = 1.125 Å) and a MAR300 imaging-plate area detector. A comparable 2.5 Å data set was measured at 90 K using a rotating-anode X-ray source and an R-AXIS IIc imaging-plate area detector (97.2% completeness, Rmerge = 6.9%). Molecular-replacement studies and multiple anomalous dispersion (MAD) experiments are currently in progress in order to determine the detailed three-dimensional structure of IXT6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444999013517
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  • 3
    Electronic Resource
    Electronic Resource
    Crystallization and preliminary X-ray analysis of α-D-glucuronidase from Bacillus stearothermophilus T-6 (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 869-872 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: α-D-Glucuronidases cleave the α-1,2-glycosidic bond of the 4-O-methyl-α-D-glucuronic acid side chain in xylan. Of the xylan-debranching hydrolases, these enzymes are the least studied and characterized. The α-glucuronidase gene (aguA) from Bacillus stearothermophilus T-6 has been cloned, sequenced and overproduced in Escherichia coli. The gene encodes for a protein of 679 amino acids with a calculated molecular weight of 78480 and a pI of 5.42. α-Glucuronidase T-6 shows high homology to the α-glucuronidases of Thermotoga maritima (60% identity) and of Trichoderma reesei (44% identity). Based on the amino-acid sequence similarity, it is likely that these enzymes represent a new class of glycosyl hydrolases. Crystallographic studies of α-glucuronidase T-6 were initiated to study the mechanism of catalysis, as well as to provide a structural basis for rational introduction of enhanced thermostability by site-specific mutagenesis. In this report, the crystallization and preliminary crystallographic characterization of the native α-glucuronidase T-6 enzyme is described. Two crystal forms were found suitable for detailed crystal structure analysis. The T1 form was obtained by the vapour-diffusion method using PEG 4000 as a precipitant and 2-propanol as an organic additive. The crystals belong to a primitive tetragonal crystal system (space group P41212 or P43212) with unit-cell dimensions a = b = 76.1 and c = 331.2 Å. These crystals are mechanically strong, are stable in the X-ray beam and diffract X-rays to better than 2.4 Å resolution. A full 3.0 Å resolution diffraction data set (97.3% completeness, Rmerge 9.8%) has recently been collected on one crystal at room temperature using a rotating-anode X-ray source and an R-AXIS IIc imaging-plate detector. The M1 form was obtained and characterized by similar techniques. The best crystallization occurred at a slightly lower pH and a lower concentration of 2-propanol. The crystals belong to a primitive monoclinic crystal system (space group P21) with unit-cell dimensions a = 65.8, b = 127.4, c = 96.6 Å and β = 97.9°. These crystals are also quite strong and stable, and diffract to better than 2.8 Å resolution. A full 2.8 Å resolution diffraction data set (96.2% completeness, Rmerge 7.6%) has recently been collected on one crystal at room temperature using the same R-AXIS IIc setup. Both forms are currently being used to obtain crystallographic phasing via isomorphous heavy-atom derivatives and selenomethionine MAD experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444998012918
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  • 4
    Electronic Resource
    Electronic Resource
    Structure of a family IIIa scaffoldin CBD from the cellulosome of Clostridium cellulolyticum at 2.2 Å resolution (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 1560-1568 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of the family IIIa cellulose-binding domain (CBD) from the cellulosomal scaffoldin subunit (CipC) of Clostridium cellulolyticum has been determined. The structure reveals a nine-stranded jelly-roll topology which exhibits distinctive structural elements consistent with family III CBDs that bind crystalline cellulose. These include a well conserved calcium-binding site, a putative cellulose-binding surface and a conserved shallow groove of unknown function. The CipC CBD structure is very similar to the previously elucidated family IIIa CBD from the CipA scaffoldin of C. thermocellum, with some minor differences. The CipC CBD structure was also compared with other previously described CBD structures from families IIIc and IV derived from the endoglucanases of Thermomonospora fusca and Cellulomonas fimi, respectively. The possible functional consequences of structural similarities and differences in the shallow groove and cellulose-binding faces among various CBD families and subfamilies are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444900012889
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  • 5
    Electronic Resource
    Electronic Resource
    TCF mill trial on softwood pulp with Korsäs thermostable and alkaline stable xylanase T6 (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 13 (1994), S. 0 
    Details
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Use of hemicellulases, including xylanases, for delignification in the paper industry has been slowed down by the lack of large-scale availability of enzymes which are active at a high pH (above 8) and a high temperature (above 60°C), conditions prevailing in many bleaching processes. During the past years, acidic or neutral hemicellulases, working at temperatures below 60°C, were used in most mill experiments. The Korsäs T6 xylanase from Bacillus stearothermophilus, which is active at a pH above 9.0 and at a temperature above 65°C, was produced on a large scale in collaboration with Gist-brocades and was employed on a full scale mill trial to produce a Total Chlorine chemical-Free (TCF) pulp from softwood. The bleaching sequence used was (OO)BQQPP. where O stands for oxygen delignification. B for the enzymatic treatment, Q for the chelating agent step and P for the hydrogen peroxide step. The enzyme bleaching step was performed during a period of 4 h at 63 ± 1°C and pH 8.7 ± 0.1. The results of the mill trial show that the TCF pulp produced had a brightness of 78% ISO and, at the same time, it preserved the same strength properties as chlorine dioxide-bleached pulp. The saving of hydrogen peroxide was 20%. The results on brightness, strength and chemical saving of this first full scale trial with T6 xylanase indicate that, after optimization, a TCF bleaching sequence including an enzymatic step with a xylanase working at a high pH and a high temperature, such as T6 xylanase, can be used to produce a high-strength bleached pulp. The advantages of a high pH and a high temperature enzymatic bleaching step are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6976.1994.tb00055.x
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  • 6
    Electronic Resource
    Electronic Resource
    The ywad gene from Bacillus subtilis encodes a double-zinc aminopeptidase (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 243 (2005), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The yet uncharacterized ywad gene from Bacillus subtilis has been cloned and overexpressed in Escherichia coli. The gene product (BSAP) was purified and shown to be an aminopeptidase. The activity of BSAP was optimal at pH 8.4, the enzyme was stable for 20 min at 80 °C and its activity was not affected by serine protease and aspartic protease inhibitors, but was completely diminished by the Zn-chelator 1,10-phenanthroline. ZnCl2 was able to restore activity, and the binding stochiometry of zinc to apo-BSAP indicated two Zn ions per protein molecule. BSAP exhibited high preference toward p-nitroanilide derived Arg, Lys, and Leu synthetic substrates resulting in kcat/Km values of 1–5 × 101 s−1 mM−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsle.2004.12.001
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  • 7
    Electronic Resource
    Electronic Resource
    Delignification of wood pulp by a thermostable xylanase from Bacillus stearothermophilus strain T-6 (1992)
    Springer
    Biodegradation 3 (1992), S. 207-218 
    Details
    ISSN: 1572-9729
    Keywords: xylanase ; biobleaching ; thermostable ; Bacillus stearothermophilus ; constitutive mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract During the bleaching of wood pulp for the paper industry, large amounts of chlorinated aromatic compounds are produced and released into the environment. These compounds are extremely toxic and are a major source of pollution. The paper and pulp industry is seeking for alternative methods for bleaching pulp. One such method involves the use of hemicellulases to release the colored lignohemicellulose. We have isolated and characterized several thermophilic bacteria which produce xylanases. One such strain, T-6, produced high levels of extracellular xylanase, free of cellulase and proteinase activities. Strain T-6 was classified as a strain of Bacillus stearothermophilus and was able to grow on defined medium containing xylose, methionine and asparagine at 65 °C. Xylanase activity was induced by either xylose or xylan; no activity was detected with other carbon sources, such as glycerol, acetate, lactose, glucose, maltose, fructose, mannose, galactose or sucrose. Xylanase constitutive mutants were obtained following mutagenesis and detection on p-nitrophenol β-d-xylopyranoside containing agar plates. Xylanase T-6 was produced on large scale, and was purified and concentrated by a single adsorption-desorption step from a cation exchanger. The overall purification yield of a 1000 liter fermentation was 45%, resulting in a 98% pure enzyme. Xylanase T-6 was shown to partially remove lignin from unbleached pulp at 65 °C and pH 9.0, without loss in pulp viscosity. The enzyme-treated pulp was used to make handsheets that had higher brightness than untreated pulp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00129084
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  • 8
    Electronic Resource
    Electronic Resource
    Optimization of protein-production by the baculovirus expression vector system in shake flasks (1992)
    Springer
    Applied microbiology and biotechnology 37 (1992), S. 74-78 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Shake flasks were successfully employed for the cultivation of Spodoptera frugiperda (Sf-9) insect cells and for the production of \-galactosidase, a recombinant model protein, utilizing the baculovirus expression vector system. The culture doubling time and maximal cell density were 20 h and 5 × 106 cells/ml respectively. The optimal liquid volumes for flasks rotating at 100 rpm were 25–40% of the flask total volume. Enzyme production (about 600 mg/l) was best at a multiplicity of infection of between 1 and 20 and at a cell density at time of infection of 0.7 × 106 cells/ml. At a rotation speed of 100 rpm, Pluronic F-68 had no effect on growth and enzyme production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00174206
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization and delignification activity of a thermostable α-l-arabinofuranosidase from Bacillus stearothermophilus (1993)
    Springer
    Applied microbiology and biotechnology 40 (1993), S. 57-62 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Bacillus stearothermophilus L1 was isolated by enrichment culture using an alkaline extract of pulp as the carbon source at 65°C and pH 9.0. The bacterium produced extracellular xylanase and α-l-arabinofuranosidase (EC 3.2.1.55). The xylanase activity was high when the cells were grown in the presence of d-xylose, whereas the arabinofuranosidase activity was high when grown in media containing l-arabinose. The arabinofuranosidase was purified 59-fold with an 80% yield by DEAE Sephacel and Sephadex G-100 chromatography. The purified enzyme had an apparent molecular mass of 110 000 kDa and consisted of two subunits of 52 500 kDa and 57 500 kDa. Using p-nitrophenyl-α-l-arabinofuranosidase as the substrate, the enzyme had a Michaelis constant (K m) of 2.2 × 10−4 m, maximum reaction velocity (Vmax) of 11o μmol min−1 mg−1, temperature optimum of 70°C and pH optimum of 7.0 (50% activity at pH 8.0). The enzyme was specific for the furanoside configuration. The purified enzyme partially delignified softwood Kraft pulp. Treatment of the pulp with 38 units ml−1 of α-l-arabinofuranosidase at 65°C for 2 h at pH 8.0 and 9.0 led to lignin releases of 2.3% and 2.1%, respectively. The enzyme acted synergistically with a thermophilic xylanase in the delignification process, yielding a 19.2% release of lignin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170429
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  • 10
    Electronic Resource
    Electronic Resource
    Unmasking of surface components by removal of cell-associated emulsan from Acinetobacter Sp. RAG-1 (1988)
    Springer
    Applied microbiology and biotechnology 28 (1988), S. 93-99 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Acinetobacter calcoaceticus RAG-1 cells lacking the emulsan capsule on the cell surface were obtained by two methods; a) by selecting for mutants that lack emulsan with a specific phage and b) by removal of the emulsan capsule from wild type cells with a specific emulsan depolymerase. Emulsan deficient cells obtained by either method become deficient in the adsorption of phage ap3 and sensitive to a newly isolated bacteriophage, nø. When RAG-1 cells were first treated with emulsan depolymerase and subsequently incubated without the enzyme, regeneration of the cell-associated emulsan was correlated with an increase in phage ap3 adsorption and an inhibition in phage nø adsorption. By partial regeneration of cell surface emulsan, a physiological state was obtained in which RAG-1 cells were sensitive to and efficiently adsorbed found phages. Enzyme-treated RAG-1 cells were found to be more adherent to hexadecane than the untreated RAG-1 cells. The data indicate that in addition to its function as the ap3 receptor, cell-associated emulsan masks the expression of other cell-surface determinant(s) which function(s) as: (i) receptor for bacteriophage nø, and (ii) cell-surface sites which enhance adherence to hydrophobic surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00250505
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