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Kosmos
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2006
|
vol. 55
|
issue 4
307-320
EN
Research concerning extremophilic microorganisms have appreciably extended our knowledge about the life limits. Psychrophiles, which are coldadapted microorganisms (some thrive even at -20°C) rank the first in abundance to the other groups of extremophiles. They populate the harshest environments on Earth, like permafrost, marine and glaciers ice, the highest parts of mountains, clouds and stratosphere. Psychrophiles have developed numerous molecular adaptations, without which they would not be able to persist in cold biotops. They produce protective exopolymers and low molecular weight cryoprotectants, polyunsaturated and branched fatty acids, which provide the appropriate fluidity of cell membranes — essential for the communication with the environment, and different sorts of proteins, like ice nucleating proteins, cold shock and cold acclimation proteins and enzymes, characterized by molecular and kinetic adaptations to catalysis of metabolic reactions at low temperatures. All these biomolecules are extremely interesting for biotechnologists because they can either widen the assortment of products applicable to industry and medicine or be valuable molecular tools to be used in biotechnology for the manufacture of these products. The properties of psychrophilic microorganisms imply that development of life is possible also in some extraterrestrial environments.
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2005
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vol. 52
|
issue 4
781-787
EN
The gene encoding β-D-galactosidase from Pyrococcus woesei was PCR amplified, cloned, expressed in Escherichia coli under the control of an inducible T7 promoter, purified and characterized. The expression system was developed by the construction of recombinant plasmid, based on the high copy number pUET1 vector, giving four times more efficient expression of P. woesei β-D-galactosidase (20 mg of enzyme from 1 liter of culture) than that obtained from a previously constructed one. The recombinant enzymes were purified in a two-step procedure: double heat-denaturation of E. coli cell proteins and affinity chromatography on p-aminobenzyl 1-thio-β-D-galactopyranoside-agarose. To achieve efficient purification of P. woesei β-D-galactosidase by immobilized metal-ion affinity chromatography (IMAC), a His-tag was placed either at the N- or the C-terminal of the coding sequence. The obtained fusion proteins revealed the same specific activity of approximately 5400 U/mg, which was 10 times lower than the wild-type β-D-galactosidase (51100 U/mg). The activity of P. woesei β-D-galactosidase was enhanced by thiol compounds, Mg2+ ions and D-galactose, and was inhibited by heavy metal ions and D-glucose, while Ca2+ ions had no effect.
EN
We cloned and sequenced the cspA-like gene from a psychrotrophic Antarctic soil-dwelling bacterial strain Psychrobacter sp. B6. The gene is 213 bp long and shows 99% and 98% sequence identity with the Psychrobacter cryohalolentis K5 gene encoding a cold-shock DNA-binding domain protein and the Psychrobacter arcticus transcriptional regulator-CspA gene, respectively. The protein encoded by the Psychrobacter sp. B6 cspA-like gene shows 100% identity with the two proteins mentioned above, and also 61% sequence identity with CspB from Bacillus subtilis and Csp from Bacillus caldolyticus, and 56% - with Escherichia coli CspA protein. A three-dimensional model of the CspA-like protein from Psychrobacter sp. B6 was generated based on three known structures of cold shock proteins: the crystal structure of the major cold shock protein from Escherichia coli (CspA), the NMR structure of the latter protein, and the NMR structure of Csp from Thermotoga maritima. The deduced structure of the CspA-like protein from Psychrobacter sp. B6 was found to be very similar to these known structures of Csp-like proteins.
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