We studied the mutation effect of subsites -3(Lys47), -7(146-152), and cyclization center (Tyr195) in active domain on product specificity of alpha-cyclodextrin glucanotransferase (alpha-CGTase) from Paenibacillus macerans sp. 602-1. The Lys47 was replaced by Thr47 and Tyr195 by Ile195, and the amino acids from 146 to 152 were replaced by Ile (named as delta6). All these mutant alpha-CGTases were actively expressed in E. coli BL21. Compared with the wild-type alpha-CGTase, the starch-degrading activities of all the mutant enzymes were declined. For mutant Y195I, the percentage of alpha-CD was decreased from 68% to 30%, and beta-CD was raised from 22.2% to 33.3%. Interestingly, gamma-CD was increased from 8.9% to 36.7% and became the main product, while the actual yield was increased from 0.4 g/L to 1.1 g/L. Mutant K47T and delta6 still produced alpha-CD as main product though the percentage of beta- and gamma-CD increased. Purified Y195I CGTase showed similar optimum temperature with the wild-type alpha-CGTase, but its optimum pH shifted from 5.0 to 6.0 with better pH stability. In summary, mutant Y195I CGTase has the potential to produce gamma-CD as the main product.
Escherichia coli ; genetics ; metabolism ; Glucosyltransferases ; genetics ; metabolism ; Mutant Proteins ; genetics ; metabolism ; Mutation ; Paenibacillus ; enzymology ; Recombinant Proteins ; genetics ; gamma-Cyclodextrins ; metabolism

To investigate the mechanism of high product specificity of gamma-clodextrin glucanotransferase (CGTase) from alkalophilic Bacillus clarkii 7364, we aligned protein sequence and structure model, found out that loss of 6 amino acids at subsite -7 probably affected its product specificity. Using overlapping PCR method, we inserted 6 amino acids into subsite -7 of CGTase. The mutant CGTase gene was ligated with pET-20b (+) and expressed in Escherichia coli BL21 (DE3). The extracellular recombinant enzyme was used to transform soluble starch into cyclodextrins (CDs). HPLC analysis results show that, compared to wild CGTase, the gamma-CDs produced by mutant enzyme decreased from 76.0% to 12.5%, whereas the ratio of alpha- and beta-CDs increased from 8.7% and 15.2% to 37.5% and 50%. The possible mechanism was that, compared to alpha-, beta-CGTase, wild gamma-CGTase lacks 6 amino acids in its subsite -7. This conformation provided more space for glucose combination and was thus advantageous for forming gamma-CD. When the 6 amino acids were inserted into the subsite -7 of wild gamma-CGTase, the space to bind with glucose reduced and consequently resulted in less gamma-CD production.
Bacillus ; enzymology ; genetics ; Escherichia coli ; genetics ; metabolism ; Glucosyltransferases ; biosynthesis ; genetics ; Mutant Proteins ; biosynthesis ; genetics ; Recombinant Proteins ; biosynthesis ; genetics

Apolipoprotein A-I-Milano(AIM), a natural variant, not only inhibits the initiation and progression of atherosclerosis, but also makes the preexisting atherosclerotic lesions regress. AIM gene, at which N-terminal codens were optimized, was subcloned into the expression vector of pET22b. Recombiant plasmids were transformed into E. coli strain BL21 (DE3) and induced with IPTG. The expressed apoliprotein A-I-Milano was soluble in E. coli and was about 38% of total cell lysate. Purified by Butyl Sepharose 4F. F hydrophobic chromatography and Q Sepharose H.P. anion exchange chromatography, followed by ultrafiltration with Vivaspin 20 (30 000MW), AIM monomer was obtained in a purity of more than 95%. Activity assay of binding of AIM monomer to lipid indicates that association of AIM monomer with DMPC is slower than normal apoA-I but DMPC number associated by AIM monomer is more than by apoA-I. This results will be important for studying structure, function of AIM, specially clinical application.
Apolipoprotein A-I ; biosynthesis ; genetics ; Escherichia coli ; genetics ; metabolism ; Humans ; Mutant Proteins ; biosynthesis ; genetics ; Recombinant Proteins ; biosynthesis ; genetics ; Solubility

OBJECTIVETo study the over-expression of mutant p53 protein in non-mucinous adenocarcinoma in-situ (NMAIS) and invasive adenocarcinoma, NOS of lung.

METHODSImmunohistochemical study for p53 protein was performed on 17 cases of NMAIS and 70 cases of invasive adenocarcinoma, NOS of lung. The difference in p53 over-expression between the two tumor subtypes was analyzed.

RESULTSThe over-expression of mutant p53 protein was observed in 0 case (0%) of NMAIS and 37 cases (52.9%) of invasive adenocarcinoma, NOS of lung. The difference was of statistical significance (P = 0.000).

CONCLUSIONMutant p53 protein over-expression may play a role in the progression of NMAIS to invasive adenocarcinoma, NOS.

Adenocarcinoma ; metabolism ; Adenocarcinoma in Situ ; metabolism ; Humans ; Immunohistochemistry ; Mutant Proteins ; genetics ; metabolism ; Tumor Suppressor Protein p53 ; genetics ; metabolism

Efforts on directed evolution of sortase A to optimize its catalytic properties have been undertaken and shown the promise. To facilitate screening of sortase A mutants with expected catalytic properties, a novel ligation efficiency monitoring system, including reporter substrates GFP-LPETG and GGGYK-Biotin, was developed. GFP-LPETG, wild type sortase A, and a recently reported high activity sortase A mutant were prepared recombinantly from Escherichia coli BL21 (DE3). Taking advantage of the newly designed reporter system, the ligation efficiency catalyzed by wild type and mutant form of sortase A could be sensitively monitored via SDS-PAGE directly. Consistent with previous report, the mutant sortase A displayed much higher catalytic activity compared to wild type enzyme, indicating the new reporter system is easily and fast handled and sensitive. The application of this reporter system into systemic screening will facilitate future directed optimization of sortase A.
Aminoacyltransferases ; genetics ; metabolism ; Bacterial Proteins ; genetics ; metabolism ; Biocatalysis ; Biotin ; Cysteine Endopeptidases ; genetics ; metabolism ; Electrophoresis, Polyacrylamide Gel ; Escherichia coli ; Genes, Reporter ; Ligation ; Mutant Proteins ; genetics ; metabolism

Glucose-regulated protein 75 (Grp75) binds to p53 and inhibits its nuclear translocation, and thus plays a role in cell protection. To investigate whether the binding of Grp75 and p53 would influence the viability of cells, we constructed the eukaryotic expression vector of Grp75 deletion mutant. The deletion mutant gene was obtained by SOE-PCR (gene splicing by overlap extension) and then linked to the pcDNA3.0 vector. The constructed specific expression vector, pcDNA3.0/Grp75(Δ253-282), was identified by restriction enzymes and sequencing. Then we used liposome to transfect the specific vector into PC12 cells. The stable cell strain PC12/Grp75(Δ253-282)(+) was selected by G418 (1 mg/mL). Semi-quantitative RT-PCR and Western blot showed that Grp75 mRNA and protein expressions in PC12/Grp75(Δ253-282)(+) cells were higher than those in PC12 cells. The viability of cells undergoing 0 h, 3 h, 9 h, 18 h and 36 h of glucose deprivation respectively was measured by MTT assay. The results showed that the cell viability of PC12/Grp75(+) group was significantly higher than that of the other two groups, and the cell viability of PC12/Grp75(Δ253-282)(+) group was significantly higher than that of the PC12 group (P<0.05). Hoechst33324 staining was employed to detect cell apoptosis and the results were consistent with the MTT assay results. Western blot results indicated that the expression of p53 in PC12/Grp75(+) cells was lower than those in the other two groups, which might be due to the overexpression of Grp75. These results suggest that the protective role of Grp75 is partly associated with its binding to p53. The above results suggest that Grp75 deletion mutation could to some extent reduce the viability of cells.
Animals ; Gene Deletion ; Genetic Vectors ; HSP70 Heat-Shock Proteins ; genetics ; metabolism ; Membrane Proteins ; genetics ; metabolism ; Mutant Proteins ; genetics ; metabolism ; PC12 Cells ; Rats ; Transfection

In order to improve the thermostability of the Penicillium expansum Lipase (PEL), the lipase encoding genes was mutated by site-directed mutagenesis. A recombinant vector pAO815-ep8-K55R which contain double mutant genes was constructed by overlap extension PCR using the cDNA of a random-mutant lipase ep8 (a single site mutant) as the template and two special primers were used to generate another mutation site K55R. The recombinant vector was transformed into Pichia pastoris GS115 by electroporation and the recombinant mutant GS-pAO815-ep8- K55R can secret double-mutant lipase PEL-ep8-K55R-GS into the medium when it was induced by Methanol. The yield of the double-mutant lipase is 508 u/mL, which is 81% that of the wild type lipase PEL-GS (627 u/mL) and 55% that of random-mutant PEL-ep8-GS (924 u/mL). The specific activity of double-mutant lipase is 2309.1 u/mg, which is similar to random-mutant lipase PEL-ep8-GS and the wild type lipase PEL-GS. The optimum temperature of the double-mutant lipase is same with the wild type lipase PEL-GS and random-mutant lipase PEL-ep8-GS. While the Tm of the double-mutant lipase is 41.0 degrees C, 2.3 degrees C higher than the wild type lipase PEL-GS and 0.8% higher than the random-mutant lipase PEL-ep8-GS, indicating that the double-mutant lipase PEL-ep8-K55R-GS has higher thermostability.
Electroporation ; Enzyme Stability ; Hot Temperature ; Lipase ; genetics ; metabolism ; Mutagenesis, Site-Directed ; Mutant Proteins ; metabolism ; Penicillium ; enzymology ; Pichia ; genetics ; metabolism ; Protein Engineering ; methods ; Recombinant Proteins ; biosynthesis ; genetics

Penicillium decumbens T. is an important filamentous fungus for the production of cellulases to effectively degrade lignocellulose for second generation biofuel production. In order to enhance the capability of Penicillium decumbens to produce cellulases, we constructed a creB (a deubiquitinating enzyme encoding gene) deletion cassette, and generated a creB knockout strain with homologous double crossover recombination. This mutation resulted in a detectable decrease of carbon catabolite repression (CCR) effect. The filter paper activity, endoglucanase activity, xylanase activity and exoglucanase activity of the deltacreB strain increased by 1.8, 1.71, 2.06 and 2.04 fold, respectively, when comparing with the parent strain Ku-39. A 2.68 fold increase of extracellular protein concentration was also observed. These results suggest that the deletion of creB results in CCR derepression. These data also suggest that CREB influences cellulase production of Penicillium decumbens. In generation, this study provides information that can be helpful for constructing cellulase hyper-producing strain.
Cellulase ; biosynthesis ; Endopeptidases ; genetics ; metabolism ; Gene Knockout Techniques ; Lignin ; metabolism ; Mutant Proteins ; metabolism ; Penicillium ; enzymology ; genetics ; Recombination, Genetic ; Ubiquitinated Proteins ; genetics ; Ubiquitination

Based on previous bioinformational analysis results, two Aspergillus niger lipase (ANL) mutants, ANL-Ser84Gly and ANL-Asp99Pro were constructed to screen ANL mutants with oil-water interface independence. ANL-Ser84Gly still displayed a pronounced interfacial activation, while ANL-Asp99Pro displayed no interfacial activation. The specific activity of ANL-Ser84Gly towards p-nitrophenyl palmitate (-myristate, -laurate and -decanoate) decreased by 29.8% (53.1, 60.1 and 77.1, respectively) than that of ANL, while the specific activity of ANL-Asp99Pro towards p-nitrophenyl palmitate increased by 2.2-fold. The mutation in the hinge region at both sides of the lid domain also destabilized various secondary structure factors of ANL-S84G and ANL-D99P, which resulted in a substantial decrease in thermostability. The achievement to construct oil-water interface-independent ANL mutants would help to further understand lipase interfacial activation mechanism.
Aspergillus niger ; enzymology ; genetics ; Base Sequence ; Enzyme Stability ; Fungal Proteins ; genetics ; metabolism ; Lipase ; genetics ; metabolism ; Molecular Sequence Data ; Mutant Proteins ; genetics ; Oils ; Substrate Specificity ; Water

Bacterial Outer Membrane Proteins ; chemistry ; genetics ; metabolism ; Escherichia coli Proteins ; chemistry ; genetics ; metabolism ; Glutamic Acid ; genetics ; metabolism ; Histidine ; genetics ; Hydrogen-Ion Concentration ; Ion Channel Gating ; genetics ; Lipid Bilayers ; metabolism ; Mutant Proteins ; chemistry ; genetics ; metabolism ; Mutation ; Porins ; chemistry ; genetics ; metabolism