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11.
Mosina Ntsoaki Leticia Schubert Wolf-Dieter Cowan Don A. 《Extremophiles : life under extreme conditions》2019,23(6):681-686
Extremophiles - Glycoside hydrolases, particularly cellulases, xylanases and mannanases, are essential for the depolymerisation of lignocellulosic substrates in various industrial bio-processes. In... 相似文献
12.
Production and secretion of a 28,172 Da hydrolase from Thermobifida fusca (TFH) in Bacillus megaterium MS941 and WH323 was investigated in shake flask and pH controlled bioreactors. Successful production of heterologous TFH was achieved by adapting the original tfh gene to the optimal codon usage of B. megaterium. A codon adaption index close to one was reached. The codon optimized tfh was cloned into an open reading frame with DNA sequence for the N-terminal signal peptide of B. megaterium lipase A and a C-terminal His(6)-tag, all under the control of a xylose inducible promoter. Successful TFH production and secretion were observed using batch reactor cultivations with complex medium. Expression of the tfh gene from the P(xylA) promoter and secretion of produced TFH were compared in detail to batch reactor cultivations with semi-defined growth medium. For the first time, significant TFH secretion was achieved using a semi-defined medium in glucose limited fed batch cultivations yielding 10-fold higher cell densities compared to LB medium cultivation. Comparable volumetric TFH activities were obtained for both cultivation strategies. Surprisingly, measured specific TFH activities exhibited drastic discrepancies between preparations from LB and semi-defined medium grown B. megaterium. TFH recovery by Ni-chelate affinity chromatography resulted in higher purification factors when LB medium was used. These results indicated that secreted TFH is favorably produced by batch cultures of B. megaterium WH323 in LB medium. 相似文献
13.
Glutamyl-tRNA reductase (GluTR) catalyzes the first step of tetrapyrrole biosynthesis in plants, archaea and most bacteria.
The catalytic mechanism of the enzyme was elucidated both by biochemical data and the determination of the high-resolution
crystal structure of the enzyme from the archaeon Methanopyrus kandleri in complex with a competitive inhibitor. The dimeric enzyme has an unusual V-shaped architecture where each monomer consists
of three domains linked by a long `spinal' α-helix. The central catalytic domain specifically recognizes the glutamate moiety
of the substrate. It bears a conserved cysteine poised to nucleophilically attack the activated aminoacyl bond of glutamyl-tRNA.
Subsequently, the thioester intermediate is reduced to the product glutamate-1-semialdehyde via hydride transfer from NADPH
supplied by the second domain. A structure-based sequence alignment indicates that catalytically essential amino acids are
conserved throughout all GluTRs. Thus the catalytic mechanism derived for M. kandleri is common to all including plant GluTRs. Mutations described to influence the catalytic efficiency of the barley enzyme can
therefore be explained.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
The MUR3 gene of Arabidopsis encodes a xyloglucan galactosyltransferase that is evolutionarily related to animal exostosins
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Madson M Dunand C Li X Verma R Vanzin GF Caplan J Shoue DA Carpita NC Reiter WD 《The Plant cell》2003,15(7):1662-1670
Xyloglucans are the principal glycans that interlace cellulose microfibrils in most flowering plants. The mur3 mutant of Arabidopsis contains a severely altered structure of this polysaccharide because of the absence of a conserved alpha-L-fucosyl-(1-->2)-beta-D-galactosyl side chain and excessive galactosylation at an alternative xylose residue. Despite this severe structural alteration, mur3 plants were phenotypically normal and exhibited tensile strength in their inflorescence stems comparable to that of wild-type plants. The MUR3 gene was cloned positionally and shown to encode a xyloglucan galactosyltransferase that acts specifically on the third xylose residue within the XXXG core structure of xyloglucan. MUR3 belongs to a large family of type-II membrane proteins that is evolutionarily conserved among higher plants. The enzyme shows sequence similarities to the glucuronosyltransferase domain of exostosins, a class of animal glycosyltransferases that catalyze the synthesis of heparan sulfate, a glycosaminoglycan with numerous roles in cell differentiation and development. This finding suggests that components of the plant cell wall and of the animal extracellular matrix are synthesized by evolutionarily related enzymes even though the structures of the corresponding polysaccharides are entirely different from each other. 相似文献
15.
Hsiao KC Brissette RE Wang P Fletcher PW Rodriguez V Lennick M Blume AJ Goldstein NI 《Proteome science》2003,1(1):1-9
Background
Hotspots are defined as the minimal functional domains involved in protein:protein interactions and sufficient to induce a biological response. 相似文献16.
Crystal structure of coproporphyrinogen III oxidase reveals cofactor geometry of Radical SAM enzymes 总被引:1,自引:0,他引:1
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'Radical SAM' enzymes generate catalytic radicals by combining a 4Fe-4S cluster and S-adenosylmethionine (SAM) in close proximity. We present the first crystal structure of a Radical SAM enzyme, that of HemN, the Escherichia coli oxygen-independent coproporphyrinogen III oxidase, at 2.07 A resolution. HemN catalyzes the essential conversion of coproporphyrinogen III to protoporphyrinogen IX during heme biosynthesis. HemN binds a 4Fe-4S cluster through three cysteine residues conserved in all Radical SAM enzymes. A juxtaposed SAM coordinates the fourth Fe ion through its amide nitrogen and carboxylate oxygen. The SAM sulfonium sulfur is near both the Fe (3.5 A) and a neighboring sulfur of the cluster (3.6 A), allowing single electron transfer from the 4Fe-4S cluster to the SAM sulfonium. SAM is cleaved yielding a highly oxidizing 5'-deoxyadenosyl radical. HemN, strikingly, binds a second SAM immediately adjacent to the first. It may thus successively catalyze two propionate decarboxylations. The structure of HemN reveals the cofactor geometry required for Radical SAM catalysis and sets the stage for the development of inhibitors with antibacterial function due to the uniquely bacterial occurrence of the enzyme. 相似文献
17.
18.
Biodegradation of Aliphatic-Aromatic Copolyesters by Thermomonospora fusca and Other Thermophilic Compost Isolates
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Ilona Kleeberg Claudia Hetz Reiner Michael Kroppenstedt Rolf-Joachim Müller Wolf-Dieter Deckwer 《Applied microbiology》1998,64(5):1731-1735
Random aliphatic-aromatic copolyesters synthesized from 1,4-butanediol, adipic acid, and terephthalic acid (BTA) have excellent thermal and mechanical properties and are biodegradable by mixed cultures (e.g., in compost). Over 20 BTA-degrading strains were isolated by using compost as a microbial source. Among these microorganisms, thermophilic actinomycetes obviously play an outstanding role and appear to dominate the initial degradation step. Two actinomycete strains exhibited about 20-fold higher BTA degradation rates than usually observed in a common compost test. These isolates were identified as Thermomonospora fusca strains. They appeared to be particularly suitable for establishment of rapid degradation tests and were used in comparative studies on the biodegradation of various polyesters. 相似文献
19.
Late Jurassic Mammals from Tendaguru, Tanzania, East Africa 总被引:1,自引:0,他引:1
Wolf-Dieter Heinrich 《Journal of Mammalian Evolution》1998,5(4):269-290
Records of Mesozoic mammals are extremely rare in Africa. The only previous record from the Upper Jurassic of Africa is a fragmentary mandible without teeth of Brancatherulum tendagurense. Here I report the discovery of two new mammals from the Upper Jurassic of Tendaguru, Tanzania. The fossils were recovered from the Middle Saurian Bed of the Tendaguru Series. A lower molar of a triconodontid mammal is described as Tendagurodon janenschi gen. et sp. nov., and a fragmentary dentary of a eupantothere as Tendagurutherium dietrichi gen. et sp. nov. The eupantothere in particular contributes to documenting the evolution of mammals during the Mesozoic. The posterior portion of the mandible of Tendagurutherium dietrichi gen. et sp. nov. shows that the angular (tympanic) bone was not yet completely separated from the dentary, a previously undocumented stage of eupantotherian middle ear evolution. 相似文献
20.
Annett Mikolasch Veronika Hahn Katrin Manda Judith Pump Nicole Illas Dirk Gördes Michael Lalk Manuela Gesell Salazar Elke Hammer Wolf-Dieter Jülich Stephan Rawer Kerstin Thurow Ulrike Lindequist Frieder Schauer 《Amino acids》2010,39(3):671-683
In order to design potential biomaterials, we investigated the laccase-catalyzed cross-linking between l-lysine or lysine-containing peptides and dihydroxylated aromatics. l-Lysine is one of the major components of naturally occurring mussel adhesive proteins (MAPs). Dihydroxylated aromatics are structurally related to 3,4-dihydroxyphenyl-l-alanine, another main component of MAPs. Mass spectrometry and nuclear magnetic resonance analyses show that the ε-amino group of l-lysine is able to cross-link dihydroxylated aromatics. Additional oligomer and polymer cross-linked products were obtained from di- and oligopeptides containing l-lysine. Potential applications in medicine or industry for biomaterials synthesised via the three component system consisting of the oligopeptide [Tyr-Lys]10, dihydroxylated aromatics and laccase are discussed. 相似文献