Expression of the thermostable carboxypeptidase Taq gene in Pichia pastoris GS115 / 生物工程学报

To express recombinant carboxypeptidase from Thermus aquaticus (Cpase Taq) in Pichia pastosis, the open reading frame coding thermostable Cpase Taq was optimized based on the preference of P. pastoris codon usage and synthesized in vitro. The novel gene was cloned into P. pastoris expression vector pHBM905A and the sequence coding 6xHis tag was fused with the ORF of Cpase Taq gene. The recombinant plasmid was named pHBM905A-Cpase Taq and transformed into P. pastoris GS 115. Transformants were induced with 1% methanol for 72 h until the enzyme yield reached 0.1 mg/ml. The enzyme was purified and its enzymatic properties were analyzed. The results showed that the specific enzyme activity reached maximum at 75 °C and pH 7.5, which was about 80 U/mg. It was the first report about the secretory expression of Cpase Taq in P. pastoris GS115. Because of its large-scale preparation, this enzyme may be applied in industrial hydrolysis of peptides into amino acids in the future.

Evaluation of biomass production, carotenoid level and antioxidant capacity produced by Thermus filiformis using fractional factorial design

A fractional factorial design 2(5-1) was used to evaluate the effect of temperature, pH, and concentrations of yeast extract, tryptone and Nitsch's trace elements on the biomass, total carotenoids and protection against singlet oxygen by carotenoid extracts of the bacterium Thermus filiformis. In addition, the carotenoid composition was determined by high-performance liquid chromatography connected to a diode array and mass spectrometer detectors (HPLC-DAD-MS/MS). The production of biomass ranged from 0.113 to 0.658 g/L, the total carotenoid from 137.6 to 1,517.4 mg/g and the protection against singlet oxygen from 4.3 to 85.1 %. Results of the fractional factorial design showed that temperature had a negative effect on biomass production and a positive effect on carotenoid content and protection against singlet oxygen, besides, high levels of pH value, concentrations of yeast extract and tryptone had a positive effect on biomass production only at lower temperatures. The main carotenoids of T. filiformis were thermozeaxanthins. In the tested conditions, changes in the levels of the variables influenced the biomass, carotenoid production, and protection against singlet oxygen, although they did not influence the carotenoid profile. The results of this study provide a better understanding on the interactions among certain nutritional and cultivation conditions of a thermophile bacterium, Thermus filiformis, on biomass and carotenoid amounts, as well as on the antioxidant capacity.

Cloning, expression and functional analysis of the genes in TPS/TPP trehalose synthetic pathway of Meiothermus ruber / 生物工程学报

By constructing the genomic DNA library of Meiothermus ruber CBS-01, the genes of trehalose phosphate synthase (TPS) and trehalose phosphate phosphatase (TPP) involved in trehalose synthesis were cloned. The genes were cloned into the plasmid pET21a, and expressed in Escherichia coli Rosetta gami (DE3). The activities of these two purified enzymes were confirmed by thin layer chromatography (TLC). Meanwhile, we tested the cellular compatible solutes of M. ruber CBS-01 under different environmental pressure, and found that under hyperosmotic pressure, this strain can accumulate trhalose-6-phosphate, but not trehalose. These results can give more insight to future research in the roles of TPS/TPP and TreS pathway.

Cloning and expression of Thermus aquaticus DNA polymerase in Escherichia coli

Thermostable DNA polymerase gene from Thermus aquaticus was cloned into constructed Taq from Thermus a Qaticus [pTTQ] plasmid using EcoRI and Sa/I sites with subsequent transformation in Escherichia coli strain [TOP10]. The use of Isopropyl-beta-D-thiogalactopyranosid [IPTG] as inducer of interested gene expression under control of the lac promoter was investigated. The optimization of enzyme induction by IPTG was determined at shake flask level to be 0.52mM at exponential growth phase. Enzyme preparation was performed by lysis the cultured cells. Afterwards, the cell suspension was incubated at 75°C to denature all heat sensitive proteins in the cell suspension that have been removed by subsequent centrifugation. Finally, the clarified supernatant containing heat resistant Taq DNA polymerase was collected and stored at -80°C. The activity of enzyme was compared with commercial Taq DNA polymerase, which remained when stored in buffer containing 50% glycerol, at -20°C. The purified enzyme had a molecular weight of 94 KDa, as estimated by SDS-PAGE and yielded appropriate enzyme activity comparing to the commercial Taq DNA polymerase

Obtención de ADN polimerasa de Thermus aquaticus en un laboratorio de mediana complejidad / Thermus aquaticus polymerase DNA's production in a medium complexity laboratory

La PCR (reaccion en cadena de la polimerasa) es una técnica de diagnóstico molecular muy sensible, capaz de revelar tan sólo una copia de ADN en una mexcla compleja del mismo. El punto central para la difusión de esta metodología fue el descubrimiento de una ADN polimerasa estable al calor aislada de Thermus aquaticus (taq ADN pol), lo cual permitió automatizar el proceso de PCR usando un ciclador térmico, sin la necesidad de una adición continua de ADN polimerasa fresca. El objetivo del trabajo fue adaptar un método para la obtención de taq ADN pol en un laboratorio hospitalario de mediana complejidad usando el equipamiento y los medios de cultivo disponibles. Con este mètodo se consiguió producir un extracto crudo de 10.000 unidades de enzima, de fácil purificación, que mostró tener muy buena actividad enzimática por lo cual es posible utilizarla en una amplia variedad de aplicaciones (PCR clásica, PCR anidada, PCR transcriptasa reversa). La actividad enzimática para estos casos fue comparable con la de la taq polimerasa que se adquiere en el mercado.

The structure-function relationship of thermostable beta-glycosidase from the thermophilic eubacterium Thermus nonproteolyticus HG102 / 生物工程学报

Beta-glycosidase (Tngly) from the thermophilic eubacterium Thermus nonproteolyticus HG102, which is a thermostable monomeric protein and adopts the (beta/alpha)8 barrel fold, is an excellent model system to be investigated for the thermostable mechanism, activity and substrate specificity. Here, based on the analysis of structural basis for thermostability of Tngly (Wang et al, 2003) and comparison of other proteins structure of homofamily, Glu164 and Glu338 may act as proton donor and nucleophile in the hydrolysis reaction respectively; proline located at N1 of alpha-helix and arginine which can form ion link may contribute to the thermostability. We aim to further identify the critical sites and the amino acid residue(s) responsible for the activity, the thermal stability and the substrate specificity. Mutations had been constructed by site-directed mutagenesis. They are Glu164Gln, Glu338Ala, Pro316Gly, Arg325Leu, Pro344Phe, Pro356Ala and Pro316Gly/Pro356Ala. All mutant proteins were purified to SDS-PAGE purity. Changes in the conformations were examined by means of CD. The Glu338Ala mutant showed no detectable hydrolysis activity, but can synthesize oligosaccharides, as expected for the residue acting as the nucleophile of the reaction. The Glu164 acts as the general acid/base catalyst in the hydrolysis reaction. Changes in stabilities of mutants compared with wild-type were determined by means of heat inactivity experiment. These results indicate that the amino acid residue of proline that is located at N1 positions of alpha-helix, and Arg325 that form salt bridge between alpha-helices 5 and alpha-helices 6, are the critical sites to protein thermostabilization.

Isolation of thermophilic bacteria Thermus sp. YBJ-1 and cloning of amylase gene / 生物工程学报

Thermophilic bacteria strain YBJ-1 was isolated from hot spring samples collected from Yangbajing, Tibet. The 16sr DNA sequence of YBJ-1 (1511bp in length) shares 98% identity with that of Thermus scotoductus strain ITI-252T. The full-length ORF of amylase gene of YBJ-1 (amyT) was amplified by PCR technique and cloned into T-vector. The complete sequence of amyT is 1767bp in length, coding for 588 amino acids. The deduced amino acids share 99% similarity with alpha-cyclodextrinse of Bacillus sterothermophilus, 96% with maltogenic amylse of Thermus. sp IM6501, and 81% with neopullulanase of Bacillus sterothermophlus.

Genome Mapping of an Extreme Thermophile, Thermus caldophilus GK24

Genome of an extreme thermophile, Thermus caldophilus GK24 has been analyzed to construct the genomic map. The genomic DNAs encapsulated in agarose gel were digested with SspI, EcoRI, SpeI, and HpaI restriction endonucleases, and then the resulting genomic DNA fragments were analyzed by pulsed-field gel electrophoresis. Its restriction map has been constructed by analyzing sizes of the restriction fragments obtained from both complete and partial digestions. The circular form of its genome was composed of about 1.98 Mbp and a megaplasmid. The genomic loci for the genes of xylose isomerase, thioredoxin, tRNA-16S rRNA, 23S rRNA, L5 ribosomal protein, ADP-glucose pyrophosphorylase, DNA-ligase, and Tca DNA polymerase were determined by both Southern hybridization and PCR.

Cloning and expression of a thermostable beta-glycosidase gene from Thermus nonproteolyticus HG102 / 生物工程学报

The gene coding for beta-glycosidase (EC3.2.1.21) from Thermus nonproteolyticus HG102 has been cloned and expressed in E. coli. The gene open reading frame was 1311 bp and it codes for 436 amino acids. The deduced amino acid sequence of the enzyme showed identity with members of glycosyl hydrolase family I. The enzyme had high content of hydrophobic amino acid (Ala 12.8%, Leu 10.9%), Arg(9.6%), Glu(9.4%) and Pro(8.0%), but low content Cys(0.45%) and Met (0.9%). From the alignment of enzyme amino acid sequence with other glycosyl hydrolase family I members, Glu164 and Glu338 were predicated as the proton donor and nucleophile group. The DNASTAR program was used to predict the secondary structure. According to the Chou-Fasman model, the enzyme has 41.4% of alpha-helics, 16.2%, beta-strands, 14.4%, beta-turns. 14 of the 35 Pro were located at the second sites of beta-turns. Hydrophobic interaction, ion bond, alpha-helics and Pro had important contribution to Tn-gly thermostability.

Accuracy of replication in the polymerase chain reaction. Comparison between Thermotoga maritima DNA polymerase and Thermus aquaticus DNA polymerase

For certain applications of the polymerase chain reaction (PCR), it may be necessary to consider the accuracy of replication. The breakthrough that made PCR user friendly was the commercialization of Thermus aquaticus (Taq) DNA polymerase, an enzyme that would survive the high temperatures needed for DNA denaturation. The development of enzymes with an inherent 3' to 5' exonuclease proofreading activity, lacking in Taq polymerase, would be an improvement when higher fidelity is needed. We used the forward mutation assay to compare the fidelity of Taq polymerase and Thermotoga maritima (ULTMATM) DNA polymerase, an enzyme that does have proofreading activity. We did not find significant differences in the fidelity of either enzyme, even when using optimal buffer conditions, thermal cycling parameters, and number of cycles (0.2 per cent and 0.13 per cent error rates for ULTMATM and Taq, respectively, after reading about 3,000 bases each). We conclude that for sequencing purposes there is no difference in using a DNA polymerase that contains an inherent 3' to 5' exonuclease activity for DNA amplification. Perhaps the specificity and fidelity of PCR are complex issues influenced by the nature of the target sequence, as well as by each PCR component.

Cloning and expression of thermus aquaticus DNA polymerase gene, using a thermo - inducible experession vector

DNA polymerase gene from Thermus aquaticus strain YT1 was amplified using VENTTH DNA polymerase and cloned under the control of lambda pr promoter and expression was induced by a shift in temperature. The culture was then sonicated, and after centrifugation the lysate was treated with polyethyleneimine followed by a salting-out step. Finally the protein was precipitated with ammonium sulfate and fractionated by gel filtration. The resulting enzyme preparation was stable and active