Search

Clostridial cellulosomes are cellulolytic complexes that are formed by highly specific interactions between one of the repeated cohesin modules present in the scaffolding protein and a dockerin module of the catalytic components. Although Clostridium thermocellum Xyn11A dockerin has a typical C. thermocellum dockerin sequence, in which two amino acid residues are species specifically conserved within the two segments of the dockerin modules, it can recognize Clostridium josui cohesin modules in a non-species-specific manner. The importance of these two conserved amino acids, which are part of the recognition site of the cohesin and dockerin interaction, was investigated by introducing mutations into the first and/or the second segments of the Xyn11A dockerin. Mutations in the first segment did not affect the interactions between dockerin and C. thermocellum and C. josui cohesins. However, mutations in the second segment prevented binding to cohesin proteins. A second round of mutations within the first segment re-established the affinity for both the C. thermocellum and the C. josui cohesins. However, this was not observed for a 'conventional' dockerin, Xyn10C. These results suggest that the combination of the first and second dockerin segments is important for the target recognition. [ABSTRACT FROM AUTHOR]

The article presents a study on the application of the gene encoding xylanase B (xynB) from Clostridium stercorarium, which belongs to family 10 glycosylhydrolases in transgenic plants such as rice and tobacco. It mentions the use of xylanases activity for enzymatic degradation while maintaining cell-free extracts of the plants to continue its normal growth. Results showed that the stable expression of xylanases can improve biofuel and crop production.

Cellulosomes are cellulolytic complexes produced by anaerobic bacteria, and are composed of a scaffolding protein and several catalytic components. The complexes are formed by highly specific interactions of one of the reiterated cohesin modules of the scaffolding protein with a dockerin module of the catalytic components. The affinities of a dockerin module of Clostridium thermocellum CelJ (Cel9D-Cel44A) for several cohesin modules from C. thermocellum and Clostridium josui scaffolding proteins were quantitatively measured by surface plasmon resonance analysis. The recombinant CelJ dockerin-containing protein interacted with three recombinant C. josui cohesin proteins as well as recombinant C. thermocellum cohesin proteins beyond the so-called ‘species specificity’ of the dockerin and cohesin interactions. However, this protein did not recognize a second cohesin module from the C. josui scaffolding protein, suggesting that the catalytic components are not necessarily arranged randomly on a scaffolding protein in native cellulosomes. [ABSTRACT FROM AUTHOR]

The article presents a study on expression of cbnA gene from soil bacterium Ralstonia eutropha NH9 in hybrid poplar and the conversion of three chlorocatechol to two-chloro-cis, cis-muconate in transgenic poplar calli. It undergoes two representation, one on moderate and one on high enzymatic activity and hybridization. Transgenic calli was found out to produce active chlorocatechol dioxygenase protein. Moreover, expression of cbnA gene presents that hybrid poplar can be used for bioremediation.

The article explores brachybacterium strain produces a malto-oligosaccharide-forming amylase. The structural gene encoding the amylase from strain was cloned and sequenced. The enzyme hydrolyzed starch to produce maltotriose primarily. This content improves product selectivity in water-miscible organic solvents.

The article discusses a study which characterized the dihydrolipoyl dehydrogenase in the diaphorase activity of Clostridium kluyveri. It conducted ultraviolet-visible adsorption spectrum and thin layer chromatography analysis for the characterization of bfmBC gene. The enzyme contained a noncovalently but tightly attached flavin adenine dinucleotide (FAD) molecule. The recombinant bfmBC gene catalyzed the oxidation of dihydro-lipoamide with nicotinamide AD as a specific electron acceptor.

The article reports on results of a study of cloning and expression of a Clostridium klyveri gene responsible for diaphorase activity. A description of the study design and method is presented. The study concluded that recombinant enzyme rDiaA showed NADH/NADPH diaphorase activity with 2,6-dichlorophenolindophenol and nitro blue tetrazolium.

The article reports on results of a study of the effect of carbon sources on the induction of xylanolytic-cellulolytic multienzyme complexes in Paenibacillus curdlanolyticus strain B-6. A description of the experimental set-up and measurement methods is presented. The study concluded that multienzyme complexes of P. curdlanolyticus B-6 consisted of the main enzymes and non-enzymatic subunits.

The article examines the possibility of module interaction in the thermal unfolding of different modular architectures. It details the construction of four truncated proteins from Clostridium stercorarium Xyn10B. The findings present the first reported case in which differences in thermal unfolding units and mechanisms were derived from differences in the modular architectures of proteins.

The article describes the high-level secretion of Bacillus halodurans recombinant xylanase Xyn11A in the yeast Kluyveromyces lactis and its functional properties. According to the authors, the choice of strain background, vector system and promoter for heterologous protein expression in the yeast is of particular importance in terms of yield maximization. They add the Xyn11A showed a specific activity of 628 U/mg-protein on birchwood xylan, but no cellulase or β-xylosidase activity.

A novel chitinase gene chiC of Clostridium paraputrificum M-21, a chitinolytic and hydrogen-gas-producing bacterium, was characterized along with its translated product. The chi18C gene encodes 683 amino acids (signal peptide included) with a deduced molecular weight of 74,651. Chi18C is a modular enzyme composed of a family-18 catalytic module of glycoside hydrolases, two reiterated modules of unknown function, and a family-12 carbohydrate-binding module. Recombinant Chi18C was active toward soluble and insoluble chitin preparations, and synthetic substrates such as 4-methylumbelliferyl-β- d- N-N′ -N″-triacetylchitotriose, but not active toward 4-MU- N-acetylglucosamine or 4-MU-β- d- N-N′-diacetylchitobioside. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunological analyses suggested that the expression of chi18C was inducible with chitinous substrates and that Chi18C was secreted into the culture medium. A possible role of Chi18C in the chitinolytic system of C. paraputrificum M-21 is discussed. [ABSTRACT FROM AUTHOR]

The article presents a study that identifies a catalytic residue of Clostridium paraputrificum N-acetyl-β-D-glucosaminidase 3A (Nag3A), an enzyme classified in family 3 of the glycoside hydrolases. Mutations were introduced into highly conserved residues to identify catalytic residues of such enzyme. Escherichia coli strains, which were grown at 37 degrees celsius and supplemented with appropriate antibiotics, were used as the host for expression of the recombinant proteins from plasmids.

The article presents a study on clostridium stercorarium and its enzymatic components in Japan. The bacteria's modular enzyme is basically composed in 2 hypothetical families of a polysaccharide lyases, the catalytic modules 9-1 (CM9-1) and CM9-2. In the study, the modular enzymes respond to bonding of calcium ions and showed high activity to polygalacturonic acid but revealed lesser reaction towards pectin.

The article investigates the functions of family-22 carbohydrate-binding modules (CBM) in clostridium josui Xyn10A. Enzymes and binding assays characterizes recombinant proteins. Glycoside hydrolases sorts into families based on the amino acid sequence similarities of their catalytic modules. The primary role of CBM is to place the enzyme on the substrate, resulting in an increase in substrate concentration around the enzyme.

The article discusses the result of the study regarding a novel thermophilic pectate lyase containing catalytic modules of Clostridium stercorarium, in Japan. The pectase lyase Pel9A was encoded by C. stercorarium F-9 pel9A gene. The family-9 catalytic modules of polysaccharide lyases include CM9-1 and CM9-2, derived from a modular enzyme, which is the mature form of Pel9A. This enzyme required calcium ion for its activity and showed a higher activity toward polygalacturonic acid but lower toward pectin.

Investigates the function of family-9 and family-22 carbohydrate-binding-modules (CBM) in a modular β-1,3-1,4-glucanase/xylanase derived from Clostridium stercorarium Xyn10B. Comparison of the enzymatic properties of truncated enzyme of two family-22 CBM and the catalytic module; Role of the addition of family-22 CBM to rCM and rCM-CBM9 in shifting the optimum temperature.

Abstract: A [Fe]-hydrogenase gene (hydA) was cloned from Clostridium paraputrificum M-21 in Escherichia coli using a conserved DNA sequence of clostridial hydrogenase genes amplified by PCR as the probe. The hydA gene consisted of an open reading frame of 1749 bp encoding 582 amino acids with an estimated molecular mass of 64,560 Da. It was ligated into a shuttle vector, pJIR751, originally constructed for Clostridium perfringens and E. coli, and expressed in C. paraputrificum. Hydrogen gas productivity of the recombinant increased up to 1.7-fold compared with the wild-type. In the recombinant, overexpression of hydA abolished lactic acid production and increased acetic acid production by over-oxidation of NADH, which is required for reduction of pyruvic acid to lactic acid in the wild-type. [Copyright &y& Elsevier]

Cites a study determining the role played by family-22 carbohydrate-binding molecule (CBM) in Clostridium thermocellum xylanase Xyn10C. Identification of CBM as a family-10 catalytic molecule of the glycosidase hydrolases responsible for cellulosome assembly from the N-terminus; Ability of recombinant CBM to show an affinity for amorphous celluloses and insoluble and soluble xylan or β-1,3-1,4-glucan; Contribution of Xyn10C in the binding of the enzyme to the substrates and in the stability of the catalytic module polypeptide in the presence of the substrate.

Describes the cloning and sequencing of new Ruminococcus albus endoglucanase genes cel5D and cel9A encoding family-5 and family-9 endoglucanases. Purification of truncated derivatives of cel5D from Escherichia coli recombinants; Presence of a cellulosome; Interaction between the dockerin modules of the catalytic components and the repeated cohesin modules of the scaffolding protein.

Describes the construction and purification of a dockerin polypeptide and a cohesin polypeptide. Interaction between a Type-II dockerin domain and a Type-II cohesin domain from Clostridium thermocellum cellulosome; Determination of the affinity constants of the interaction between the dockerin polypeptide and the cohesin polypeptide by the surface plasmon resonance method; Dissociation value.