Two-step transpeptidation of the insulin precursor expressed in Pichia pastoris to insulin ester via trypsin-catalyzed cleavage and coupling

Insulin precursor fusion protein expressed in Pichia pastoris is a single-chain protein with a spacer peptide (EEAEAEAEPK) localized at its N-terminal. Currently, the one-step transpeptidation reaction with low yield and high cost is generally employed to convert the insulin precursor fusion protein into human insulin ester. In this study, a two-step transpeptidation reaction was proposed separating the cleavage step from the coupling step so that each reaction was performed under its optimal conditions. Using this method, the total efficiency doubled and the reaction time was shortened compared with the one-step method. In addition, the amount of O-t-butyl-l-threonine t-butyl ester and trypsin dosages were reduced by 50% and 75%, respectively. This two-step transpeptidation strategy was simple and efficient and could be used for the pharmaceutical production of human insulin.

Construction of pPIC9 Recombinant Vector Containing Human Stem Cell Factor

PURPOSE

Various cytokine regulates hematopoesis; they promote number of stages in stem cells biology such as proliferation, differentiation and endurance. Biological effects of SCF, as a hematopoietic cytokine; is triggered by binding to its ligand c-kit. Potential therapeutic applications of SCF include hematopoietic stem cell mobilization, exvivo stem/progenitor cell expansion, gene therapy, and immunotherapy. In this study we tried to construct of pPIC9 recombinant vector containing human SCF.

METHODS

hSCF cDNA was amplified by PCR and both hSCF cDNA and pPIC9 as yeast expression vector (shuttle vector) digested by EcoR I and Xho I restriction enzymes. Subsequent the digestion reaction, ligation reaction was carried out. In order to verifying of pPIC9 recombinant vector containing hSCF, PCR and sequence analysis was performed.

RESULTS

The construction of recombinant expression vector of pPIC9 containing hSCF cDNA was confirmed by sequencing method successfully.

CONCLUSION

rhSCF/pPIC9 vector can be transformed into the Picha pastoris yeast as a eukaryotic host in order to produce human SCF at industrial scale.

An autonomously replicating sequence for use in a wide range of budding yeasts

The initiation of DNA replication at replication origins is essential for the duplication of genomes. In yeast, the autonomously replicating sequence (ARS) property of replication origins is necessary for the stable maintenance of episomal plasmids. However, because the sequence determinants of ARS function differ among yeast species, current ARS modules are limited for use to a subset of yeasts. Here, we describe a short ARS sequence that functions in at least 10 diverse species of budding yeast. These include, but are not limited to members of the Saccharomyces, Lachancea, Kluyveromyces, and Pichia (Komagataella) genera spanning over 500 million years of evolution. In addition to its wide species range, this ARS and an optimized derivative confer improved plasmid stability relative to other currently used ARS modules.

Glycosylation characterization of recombinant human erythropoietin produced in glycoengineered Pichia pastoris by mass spectrometry

Glycosylation plays a critical role in the in vivo efficacy of both endogenous and recombinant erythropoietin (EPO). Using mass spectrometry, we characterized the N-/O-linked glycosylation of recombinant human EPO (rhEPO) produced in glycoengineered Pichia pastoris and compared with the glycosylation of Chinese hamster ovary (CHO) cell-derived rhEPO. While the three predicted N-linked glycosylation sites (Asn24, Asn38 and Asn83) showed complete site occupancy, Pichia- and CHO-derived rhEPO showed distinct differences in the glycan structures with the former containing sialylated bi-antennary glycoforms and the latter containing a mixture of sialylated bi-, tri- and tetra-antennary structures. Additionally, the N-linked glycans from Pichia-produced rhEPO were similar across all three sites. A low level of O-linked mannosylation was detected on Pichia-produced rhEPO at position Ser126, which is also the O-linked glycosylation site for endogenous human EPO and CHO-derived rhEPO. In summary, the mass spectrometric analyses revealed that rhEPO derived from glycoengineered Pichia has a highly uniform bi-antennary N-linked glycan composition and preserves the orthogonal O-linked glycosylation site present on endogenous human EPO and CHO-derived rhEPO.

Utilization of glycerin byproduct derived from soybean oil biodiesel as a carbon source for heterologous protein production in Pichia pastoris

Crude glycerol, also known as glycerin, is the main byproduct of the biodiesel industry. It has been estimated that up to 40,000 tons of glycerin will be produced each year by 2020. This study evaluated the value-added use of crude glycerol derived from soybean biodiesel preparation as a carbon source for heterologous protein production using the yeast Pichia pastoris. Eleven glycerin samples were obtained by methanolysis of soybean oil using different acids or bases as catalysts. Cell growth experiments showed that crude glycerol containing either potassium or sodium hydroxide resulted in 1.5-2 times higher final cell densities when compared to glycerol P.A. Finally, crude glycerol containing sodium hydroxide was successfully utilized for constitutive heterologous α-amylase production in P. pastoris. This study demonstrated that crude glycerol without any purification steps may be directly used as carbon source for protein production in P. pastoris.

Cloning and Expression in Pichia pastoris of a New Cytochrome P450 Gene from a Dandruff-causing Malassezia globosa

The Malassezia fungi are responsible for various human skin disorders including dandruff and seborrheic dermatitis. Of the Malassezia fungi, Malassezia globosa (M. globosa) is one of the most common in human scalp. The completed genome sequence of M. globosa contains four putative cytochrome P450 genes. To determine the roles of Malassezia P450 enzymes in the biosynthesis of ergosterol, we isolated MGL3996 gene from M. globosa chromosomal DNA by PCR. The MGL3996 gene encodes an enzyme of 616 amino acids, which shows strong similarity with known CYP52s of other species. MGL3996 gene was cloned and expressed in Pichia pastoris (P. pastoris) heterologous yeast expression system. Using the yeast microsomes expressing MGL3996 protein, a typical P450 CO-difference spectrum was shown with absorption maximum at 448 nm. SDS-PAGE analysis revealed a protein band of apparent molecular weight 69 kDa and Western blot with anti-histidine tag antibody showed that MGL3996 was successfully expressed in P. pastoris. Cloning and expression of a new P450 gene is an important step to study the P450 monooxygenase system of M. globosa and to understand the role of P450 enzymes in pathophysiology of dandruff.

Production of a defensin-like antifungal protein NFAP from Neosartorya fischeri in Pichia pastoris and its antifungal activity against filamentous fungal isolates from human infections

Neosartorya fischeri NRRL 181 isolate secretes a defensin-like antifungal protein (NFAP) which has a remarkable antifungal effect against ascomycetous filamentous fungi. This protein is a promising antifungal agent of biotechnological value; however in spite of the available knowledge of the nature of its 5'-upstream transcriptional regulation elements, the bulk production of NFAP has not been resolved yet. In this study we carried out its heterologous expression in the yeast Pichia pastoris and investigated the growth inhibition effect exerted by the heterologous NFAP (hNFAP) on filamentous fungal isolates from human infections compared with what was caused by the native NFAP. P. pastoris KM71H transformant strain harboring the pPICZαA plasmid with the mature NFAP encoding gene produced the protein. The final yield of the hNFAP was sixfold compared to the NFAP produced by N. fischeri NRRL 181. Based on the signal dispersion of the amide region, it was proven that the hNFAP exists in folded state. The purified hNFAP effectively inhibited the growth of fungal isolates belonging to the Aspergillus and to the Fusarium genus, but all investigated zygomycetous strain proved to be insusceptible. There was no significant difference between the growth inhibition effect exerted by the native and the heterologous NFAP. These data indicated that P. pastoris KM71H can produce the NFAP in an antifungally active folded state. Our results provide a base for further research, e.g., investigation the connection between the protein structure and the antifungal activity using site directed mutagenesis.

Expression of codon optimized human bone morphogenetic protein 4 in Pichia pastoris

Bone morphogenetic proteins (BMPs) are TGF-β family member proteins that have therapeutic potential. The amount of BMPs from natural resources is limited, and the production of biologically active BMPs in heterologous protein expression systems remains an obstacle for their clinical application. In this study, the DNA sequence of human BMP4 mature domain (hBMP4) was optimized according to the codon relative synonymous codon usage values in Pichia pastoris, and the A+T content in the sequence after optimization was within the range of 30% to 55%. In Pichia pastoris cultured in shake-flask, the expression level of hBMP4 protein from the optimized sequence (48 mg/L) increased fourfold in comparison with that from the native sequence (12 mg/L). Recombinant hBMP4 protein was purified by SP Sepharose and heparin affinity chromatography. The biological activities of recombinant hBMP4 were examined by measuring proliferation stimulation in cells and induction of ectopic cartilage formation in mouse models. Our results demonstrated that the optimized DNA sequence could significantly enhance hBMP4 protein expression in Pichia pastoris compared with the native sequence and produce biologically active recombinant hBMP4; this indicates the potential of this optimized sequence for bulk production of hBMP4 protein in future clinical applications.

High-level secretion of recombinant full-length streptavidin in Pichia pastoris and its application to enantioselective catalysis

Artificial metalloenzymes result from the incorporation of a catalytically competent biotinylated organometallic moiety into full-length (i.e. mature) streptavidin. With large-scale industrial biotechnology applications in mind, large quantities of recombinant streptavidin are required. Herein we report our efforts to produce wild-type mature and biotin-free streptavidin using the yeast Pichia pastoris expression system. The streptavidin gene was inserted into the expression vector pPICZαA in frame with the Saccharomyces cerevisiae α-mating factor secretion signal. In a fed-batch fermentation using a minimal medium supplemented with trace amounts of biotin, functional streptavidin was secreted at approximately 650mg/L of culture supernatant. This yield is approximately threefold higher than that from Escherichia coli, and although the overall expression process takes longer (ten days vs. two days), the downstream processing is simplified by eliminating denaturing/refolding steps. The purified streptavidin bound ∼3.2molecules of biotin per tetramer. Upon incorporation of a biotinylated piano-stool catalyst, the secreted streptavidin displayed identical properties to streptavidin produced in E. coli by showing activity as artificial imine reductase.

Atg18 lifts up from and lands on the vacuolar membrane mediated by phosphorylation of its propellers

Pichia pastoris Atg18 (PpAtg18), a member of the PROPPIN family of proteins, is localized not only to the PAS (pre-autophagosomal structure or phagophore assembly site) during autophagy but also to the vacuolar membrane during vacuolar fission. Recently we reported that the localization of Atg18 was determined by its phosphorylation level. We identified two phosphorylated regions within the ?-propeller structures of PpAtg18, whose modification affects its affinity toward phosphatidylinositol 3,5-bisphosphate [PtdIns(3,5)P 2]. The findings indicated that phosphoregulaton of Atg18 mediates the signal from various environmental stimuli and regulates its intracellular localization for vacuolar fission and autophagy.

Optimization of five environmental factors to increase beta-propeller phytase production in Pichia pastoris and impact on the physiological response of the host

Recently, we engineered Pichia pastoris Mut(s) strains to produce several beta-propeller phytases, one from Bacillus subtilis and the others designed by a structure-guided consensus approach. Furthermore, we demonstrated the ability of P. pastoris to produce and secrete these phytases in an active form in shake-flask cultures. In the present work, we used a design of experiments strategy (Simplex optimization method) to optimize five environmental factors that define the culture conditions in the induction step to increase beta-propeller phytase production in P. pastoris bioreactor cultures. With the optimization process, up to 347,682 U (82,814 U/L or 6.4 g/L culture medium) of phytase at 68 h of induction was achieved. In addition, the impact of the optimization process on the physiological response of the host was evaluated. The results indicate that the increase in extracellular phytase production through the optimization process was correlated with an increase in metabolic activity of P. pastoris, shown by an increase in oxygen demand and methanol consumption, that increase the specific growth rate. The increase in extracellular phytase production also occurred with a decrease in extracellular protease activity. Moreover, the optimized culture conditions increased the recombinant protein secretion by up to 88%, along with the extracellular phytase production efficiency per cell.

The role of N-glycosylation sites in the activity, stability, and expression of the recombinant elastase expressed by Pichia pastoris

The Pseudomonas aeruginosa elastase (PAE), produced by Pseudomonas aeruginosa (P. aeruginosa), is a promising biocatalyst for peptide synthesis in organic solvents. As P. aeruginosa is an opportunistic pathogen, the enzyme has been heterologously over-expressed in the safe and efficient host, Pichia pastoris (P. pastoris) for its industrial application. The recombinant elastase (rPAE) contains three potential N-glycosylation sites (Asn-Xaa-Ser/Thr consensus sequences), and is heterogeneously N-glycosylated. To investigate the role of N-glycosylation in the activity, stability, and expression of rPAE, these potential N-glycosylation sites (N43, N212, and N280) were mutated using site-directed mutagenesis. Specifically the asparagine (Asn, N) residues were converted to glutamine (Gln, Q). The enzymatic activity and stability of non-glycosylated and glycosylated rPAE were then compared. The results indicated that the influence of N-glycosylation on its activity was insignificant. The non- and glycosylated isoforms of rPAE displayed similar kinetic parameters for hydrolyzing casein in aqueous medium, and when catalyzing bipeptide synthesis in 50% (v/v) DMSO, they exhibited identical substrate specificity and activity, and produced similar yields. However, N-glycosylation improved rPAE stability both in aqueous medium and in 50% (v/v) organic solvents. The half-lives of the glycosylated and non-glycosylated forms of rPAE at 70°C were 32.2 and 23.1 min, respectively. Mutation of any potential N-glycosylation site was detrimental to its expression in P. pastoris. There was a 23.9% decrease in expression of the N43Q mutant, 63.6% of the N212Q mutant, and 63.7% of the N280Q mutant compared with the wild type. Furthermore, combined mutation of these sites resulted in an additional decrease in the caseinolytic activities of the mutants. These results indicated that all of the N-glycosylation sites were necessary for high-level expression of rPAE.

Expression of Pisum sativum PsAO3 gene, which encodes an aldehyde oxidase utilizing abscisic aldehyde, is induced under progressively but not rapidly imposed drought stress

Aldehyde oxidase (AO; EC 1.2.3.1) catalyzes the final step of abscisic acid (ABA) biosynthesis, which is the oxidation of abscisic aldehyde (ABAld) to ABA. Gene expression analyses indicate that the stress-induced Pisum sativum PsAOγ isoform, which effectively uses ABAld as a substrate, is encoded by the PsAO3 gene. PsAO3 was heterologously expressed in Pichia pastoris and the recombinant PsAO3 protein revealed substrate preferences highly similar to the native PsAOγ protein present in the pea leaves and roots. Both proteins prefer indole-3-aldehyde and naphthaldehyde as substrates, although high activities against abscisic aldehyde and citral were also observed. The Km values of PsAO3 for naphthaldehyde and abscisic aldehyde (4.6 and 5.1 μM, respectively) were the lowest among the substrates tested. PsAO3 activity was almost completely inhibited by potassium cyanide, diphenyleneiodonium, and methanol. Rapidly imposed drought stress did not increase the level of PsAO3 mRNA or activity of any AO isoform, although an enhanced ABA accumulation and induction of PsNCED2 and -3 (9-cis-epoxycarotenoid dioxygenase; EC 1.13.11.51) expression, both in the pea roots and leaves, was observed. During a progressively induced drought, the level of PsAO3 transcript and PsAOγ activity increased significantly in the roots and leaves, whereas ABA accumulation occurred only in the leaves where it was accompanied by induction of the PsNCED3 expression. Therefore, we suppose that next to NCED, also AO (mainly PsAOγ) might be involved in regulation of the drought-induced ABA synthesis. However, while the "constitutive activity" of PsAOγ is sufficient for the fast generation of ABA under rapid drought stress, the enhanced PsAOγ activity is required for the progressive and long-term ABA accumulation in the leaves under progressive drought stress.

Enhancement of lipase r27RCL production in Pichia pastoris by regulating gene dosage and co-expression with chaperone protein disulfide isomerase

Pichia pastoris has been successfully used in the production of many secreted and intracellular recombinant proteins, but there is still a large room of improvement for this expression system. Two factors drastically influence the lipase r27RCL production from Rhizopus chinensis CCTCC M201021, which are gene dosage and protein folding in the endoplasmic reticulum (ER). Regarding the effect of gene dosage, the enzyme activity for recombinant strain with three copies lipase gene was 1.95-fold higher than that for recombinant strain with only one copy lipase gene. In addition, the lipase production was further improved by co-expression with chaperone PDI involved in the disulfide bond formation in the ER. Overall, the maximum enzyme activity reached 355U/mL by the recombinant strain with one copy chaperone gene PDI plus five copies lipase gene proRCL in shaking flasks, which was 2.74-fold higher than that for the control strain with only one copy lipase gene. Overall, co-expression with PDI vastly increased the capacity for processing proteins of ER in P. pastoris.

Bacteriophage T7 RNA polymerase-based expression in Pichia pastoris

A novel Pichia pastoris expression vector (pEZT7) for the production of recombinant proteins employing prokaryotic bacteriophage T7 RNA polymerase (T7 RNAP) (EC 2.7.7.6) and the corresponding promoter pT7 was constructed. The gene for T7 RNAP was stably introduced into the P. pastoris chromosome 2 under control of the (endogenous) constitutive P. pastoris glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter (pGAP). The gene product T7 RNAP was engineered to contain a nuclear localization signal, which directed recombinant T7 RNAP to the P. pastoris nucleus. To promote translation of uncapped T7 RNAP derived transcripts, the internal ribosomal entry site from hepatitis C virus (HCV-IRES) was inserted directly upstream of the multiple cloning site of pEZT7. A P. pastoris autonomous replicating sequence (PARS1) was integrated into pEZT7 enabling propagation and recovery of plasmids from P. pastoris. Rapid amplification of 5' complementary DNA ends (5' RACE) experiments employing the test plasmid pEZT7-EGFP revealed that transcripts indeed initiated at pT7. HCV-IRES mediated translation of the latter mRNAs, however, was not observed. Surprisingly, HCV-IRES and the reverse complement of PARS1 (PARS1rc) were both found to display significant promoter activity as shown by 5' RACE.

Comparative performance of S-adenosyl-L-methionine biosynthesis and degradation in Pichia pastoris using different promoters and novel consumption inhibitors

The yeast Pichia pastoris is a widely used host for recombinant protein expression, and has recently been engineered for whole-cell biocatalysis. The inducible P(AOX) and constitutive P(GAP) promoters are commonly employed. In this study, the S-adenosyl-L-methionine (SAM) biosynthesis and degradation efficiency of two P. pastoris strains were compared, and novel inhibitors that suppress SAM degradation were characterized. The strains exhibited clear physiological differences. P(GAP)-Pichia showed higher transcription and activity of SAM synthetase, and the rapid cell growth led to higher levels of spermidine synthesis from SAM. In contrast, P(AOX)-Pichia synthesized higher levels of glutathione from SAM, and this strain responded to hydrogen peroxide formation during methanol utilization. Aristeromycin proved an efficient inhibitor of SAM degradation in P(AOX)-Pichia; 0.02 mg/L led to a 36.36% reduction in the ratio of glutathionine:SAM, and SAM accumulation was enhanced by 7.74% to 11.83 g/L. Ethanol was an even more efficient inhibitor of SAM consumption in P(GAP)-Pichia; 8 g/L resulted in a 73.68% decrease in the ratio of SPD:SAM, and SAM production was elevated by 54.55% to 0.17 g/L/h.

Production and secretion of Lactobacillus crispatus β-galactosidase in Pichia pastoris

Lactobacillus β-galactosidases are mostly heterodimeric proteins, which are encoded by the two overlapping genes, lacL and lacM, and produced in recombinant prokaryotic systems for higher yield. This is the first report on the expression of a heterodimeric β-galactosidase from Lactobacillus crispatus B470 in Pichia pastoris. The overlapping consecutive genes, lacL and lacM, that shared 17 nucleotides were cloned from the genomic DNA of L. crispatus. A recombinant plasmid harboring both expression cassettes of lacL and lacM was constructed and transformed into P. pastoris GS115 competent cells. Two recombinant P. pastoris strains (GSLac01 and GSLac02) showed the highest β-galactosidase activities of 24.5 and 31.0 U/ml in the culture supernatants, respectively. The recombinant β-galactosidase (LcLacLM) from GSLac02 was purified to electrphoretic homogeneity by ion-exchange chromatography and molecular sieve chromatography. Similar to most Lactobacillus β-galactosidases that operate at moderately thermophilic and weak acid to neutral conditions, LcLacLM showed optimal activity at 50°C and pH 5.5-6.5. It's the first report on functional and secretory expression of LacLM-type β-galactosidase in eukaryotic system. This strategy might be applied to the expression of other overlapping genes.

Cloning of Vibrio cholerae outer membrane protein W in Pichia pastoris

BACKGROUND AND OBJECTIVE

The outer membrane protein W (ompW) of Vibrio cholerae is involved in stimulating the immune response via induction of protective immunity. It also plays an important role in bacterial pathogenesis by increasing the adaptability of pathogenic strains. In this study we aimed to clone V. cholerae ompW gene in the strain X-33 of Pichia pastoris.

MATERIALS AND METHODS

A gene encoding ompW was cloned into the Ppicza vector downstream of alcohol oxidase promoter. Then recombinant vector was transformed into the genome of the strain X-33 of P. pastoris. After growth of zeocin-resistant transformants, clones were selected and subsequently confirmed for cloning by PCR enzymatic digestion and sequencing.

RESULTS

PCR, enzymatic digestion and sequencing showed that the ompW gene was correctly cloned into P. pastoris genome.

CONCLUSION

Results of our study showed that the methylotrophic yeast P. pastoris can be considered as an appropriate host instead of mammalian and prokaryotic systems for cloning of ompW. As far as data show, this is the first time that ompW of V. cholera is cloned into the methylotrophic P. pastoris.

Redox-regulated cargo binding and release by the peroxisomal targeting signal receptor, Pex5

In its role as a mobile receptor for peroxisomal matrix cargo containing a peroxisomal targeting signal called PTS1, the protein Pex5 shuttles between the cytosol and the peroxisome lumen. Pex5 binds PTS1 proteins in the cytosol via its C-terminal tetratricopeptide domains and delivers them to the peroxisome lumen, where the receptor·cargo complex dissociates. The cargo-free receptor is exported to the cytosol for another round of import. How cargo release and receptor recycling are regulated is poorly understood. We found that Pex5 functions as a dimer/oligomer and that its protein interactions with itself (homo-oligomeric) and with Pex8 (hetero-oligomeric) control the binding and release of cargo proteins. These interactions are controlled by a redox-sensitive amino acid, cysteine 10 of Pex5, which is essential for the formation of disulfide bond-linked Pex5 forms, for high affinity cargo binding, and for receptor recycling. Disulfide bond-linked Pex5 showed the highest affinity for PTS1 cargo. Upon reduction of the disulfide bond by dithiothreitol, Pex5 transitioned to a noncovalent dimer, concomitant with the partial release of PTS1 cargo. Additionally, dissipation of the redox balance between the cytosol and the peroxisome lumen caused an import defect. A hetero-oligomeric interaction between the N-terminal domain (amino acids 1-110) of Pex5 and a conserved motif at the C terminus of Pex8 further facilitates cargo release, but only under reducing conditions. This interaction is also important for the release of PTS1 proteins. We suggest a redox-regulated model for Pex5 function during the peroxisomal matrix protein import cycle.

Engineered Pichia pastoris for enhanced production of S-adenosylmethionine

A genetically engineered strain of Pichia pastoris expressing S-adenosylmethionine synthetase gene from Saccharomyces cerevisiae under the control of AOX 1 promoter was developed. Induction of recombinant strain with 1% methanol resulted in the expression of SAM2 protein of ~ 42 kDa, whereas control GS115 showed no such band. Further, the recombinant strain showed 17-fold higher enzyme activity over control. Shake flask cultivation of engineered P. pastoris in BMGY medium supplemented with 1% L-methionine yielded 28 g/L wet cell weight and 0.6 g/L S-adenosylmethionine, whereas control (transformants with vector alone) with similar wet cell weight under identical conditions accumulated 0.018 g/L. The clone cultured in the bioreactor containing enriched methionine medium showed increased WCW (117 g/L) as compared to shake flask cultures and yielded 2.4 g/L S-adenosylmethionine. In spite of expression of SAM 2 gene up to 90 h, S-adenosylmethionine accumulation tended to plateau after 72 h, presumably because of the limited ATP available in the cells at stationery phase. The recombinant P pastoris seems promising as potential source for industrial production of S-adenosylmethionine.

Cloning and expression of an anti-LDL(-) single-chain variable fragment, and its inhibitory effect on experimental atherosclerosis

The in vivo modified forms of low-density lipoprotein (LDL) are important for the formation of foam cells and as mediators of the immuno-inflammatory process involved in the progression of atherosclerosis. Electronegative LDL, LDL(-), is a LDL subfraction with pro-inflammatory properties that is present in human blood. To investigate possible atheroprotective effects, an anti-LDL(-) single-chain variable fragment (scFv) was expressed in the methylotrophic yeast Pichia pastoris and its activity was evaluated in vitro against macrophages and in experimental atherosclerosis in Ldlr(-/-) mice. The recombinant 2C7 scFv was produced in a yield of 9.5 mg of protein/L. The specificity and affinity of purified 2C7 scFv against LDL(-) was confirmed by ELISA. To assess the activity of 2C7 scFv on foam cell formation, RAW 264.7 macrophages were exposed to LDL(-) in the presence or absence of 2C7 scFv. The 2C7 scFv inhibited the uptake of LDL(-) by macrophages in a dose-dependent manner, and internalization of LDL(-) by these cells was found to be mediated by the CD36 and CD14 receptor. In addition, compared with untreated cells, lipid accumulation in macrophages was decreased, and the expression of Cd36, Tlr-4 and Cox-2 was downregulated in macrophages treated with 2C7 scFv. Importantly, compared with untreated mice, the treatment of Ldlr(-/-) mice with 2C7 scFv decreased the atherosclerotic lesion area at the aortic sinus. In conclusion, our data show that 2C7 scFv inhibits foam cell formation and atherosclerotic plaque development by modulating the expression of genes relevant to atherogenesis. These results encourage further use of this antibody fragment in the development of new therapeutic strategies that neutralize the pro-atherogenic effects of LDL(-).

Gene cloning of porcine adiponectin gene from adipose tissue and construction of its eukaryotic expression vector

To clone adiponectin (ADPN) gene from Shaziling porcine adipocyte and construct its eukaryotic expression vector, total RNA was extracted from subcutaneous fatty tissue. One pair of specific primers was designed by Primer 5.0 software according to the sequence of ADPN gene of porcine available in GenBank. The ADPN gene was amplified by PCR from cDNA and cloned into pMD18-T vector to construct recombinant clonal vector pMD-ADPN, sequenced and analysed. A recombinant expression plasmid pPICZaA-ADPN was constructed by subcloning the cloned ADPN gene into the linearized pPICZaA vector. Then, the plasmid pPICZaA-ADPN was expressed in Pichia pastoris (GS115) by electrotransformation. Western blot and Bradford analysis were used to determine the target protein induced by methanol. Results showed that the genome size of ADPN was 732 bp and encoded 244 amino acid, the nucleotide sequence of ADPN shared 100% identity with that of porcine available in GenBank. Western blot and Bradford analysis showed that the recombinant ADPN was expressed in GS115 correctly and has certain immune activity. The expression level of ADPN was 28.5 μg/ml. In conclusion, the recombinant ADPN could express in eukaryotic expression vector pPICZaA-ADPN constructed in this study effectively.

Optimized expression of (S)-carbonyl reductase in Pichia pastoris for efficient production of (S)-1-phenyl-1, 2-ethanediol

The recombinant (S)-carbonyl reductase (SCR) in Escherichia coli catalyzed the reduction of 2-hydroxyacetophenone to (S)-1-phenyl-1,2-ethanediol (PED) with low efficiency. In this work, its 6× histidine fusion gene his6 -scr was cloned in Pichia pastoris under the control of the AOX1 methanol inducible promoter. The heterologous protein SCR was expressed through a Mut(s) phenotype. Under the optimal conditions: pH 7.0, initial OD600 2.5, methanol daily addition concentration 1.0% and induction duration 4-5 days, the recombinant protein SCR was produced at the highest level. The enzyme activity in the cell-free exacts of P. pastoris was 0.38, which was over twofold than that of the recombinant E. coli-SCR. The enzyme was purified to homogeneity with a specific activity of 3.41 U mg(-1) , and it catalyzed the biotransformation of (S)-PED with a high optical purity of 96.9% in a high yield of 89.7% at optimum pH of 7.0. The developed effective system of P. pastoris-SCR will facilitate the preparation of pure chiral alcohol in industry.

Quantitative iTRAQ LC-MS/MS proteomics reveals the cellular response to heterologous protein overexpression and the regulation of HAC1 in Pichia pastoris

The methylotrophic yeast Pichia pastoris is an attractive platform for a plethora of recombinant proteins. There is growing evidence that host cells producing recombinant proteins are exposed to a variety of cellular stresses resulting in the induction of the unfolded protein response (UPR) pathway. At present, there is only limited information about the cellular reactions of the host cells at the level of the proteome, especially with regard to recombinant protein secretion. Here we monitored xylanase A secretion from Bacillus halodurans C-125 (xynA) in P. pastoris, using strains containing different copy numbers of the gene encoding xylanase A and co-overexpressing the gene encoding the UPR-regulating transcription factor HAC1 by applying a quantitative proteomics approach (iTRAQ-LC-MS/MS). Many important cellular processes, including carbon metabolism, stress response and protein folding are affected in the investigated conditions. Notably, the analysis revealed that strong over-expression of xynA can efficiently improve protein production but simultaneously cause an unfolded protein burden with a subsequent induction of the UPR. This limits the further improvement of protein production levels. Remarkably, constitutive expression of the gene encoding HAC1 lessens the unfolded protein burden by attenuating protein synthesis and increasing ER protein folding efficiency which is beneficial for protein secretion.

BIOLOGICAL SIGNIFICANCE

Pichia pastoris expression systems have been successfully used for over 20years in basic research and in the biotechnology industry for the production and secretion of a wide range of recombinant proteins. In particular, secretion of recombinant proteins is still one of the main reasons for using P. pastoris. It has become obvious that many protein products can lead to severe stress on the host cell when being over-expressed, thus limiting the potential yield. Detailed understanding of the physiological responses to such stresses gives rise to engineering of host cells that can better cope with the stress factors. Therefore, the regulatory mechanism of heterologous protein secretion by quantitative mass-spectrometry (MS) proteomics is a growing field and an important endeavor in improving protein annotation. Many important cellular processes, including carbon and amino acid metabolism, stress response and protein folding are affected in the over-expression strains. This data represent a first step towards a systems wide approach to assess the response with recombinant protein induced stress in P. pastoris.

Potential of Ophiostoma piceae sterol esterase for biotechnologically relevant hydrolysis reactions

The ascomycete Ophiostoma piceae produces a sterol esterase (OPE) with high affinity toward p-nitrophenol, glycerol, and sterol esters. Recently, this enzyme has been heterologously expressed in the methylotrophic yeast Pichia pastoris under the AOX1 methanol-inducible promoter (PAOX1) using sorbitol as co-susbtrate, and the hydrolytic activity of the recombinant protein (OPE*) turned out to be improved from a kinetic point of view. In this study, we analyze the effects of sorbitol during the expression of OPE*, at first added as an additional carbon source, and methanol as inducer. The O. piceae enzyme was successfully used for PVAc hydrolysis, suggesting its potential applicability in recycled paper production to decrease stickies problems.

Cloning and expression of a xylanase xynB from Aspergillus niger IA-001 in Pichia pastoris

The high-level expression of the xylanase GH11 gene from Aspergillus niger IA-001 called xynB was successfully completed in Pichia pastoris. The xynB gene encoding a mature xylanase of 225 amino acid was subcloned into the pPICZαA vector and was transformed into P. pastoris X-33 under the control of the alcohol oxidase I (AOX1) promoter. The xynB gene was ligated with a sequence encoding modified α-factor signal peptide (pPICZαmA) and the recombinant xylanase activity, which was measured 1280 U ml(-1), was 1.5-fold higher than when it was inserted into pPICZαA and was 19.39-fold greater than the native xylanase in the original strain. In a 10 L fermenter, the recombinant xylanase activity measured 10,035 U ml(-1) after 114 h. The SDS-PAGE analysis revealed that the purified xynB protein migrated as a single band with an apparent molecular weight of 24 kDa. The specific activity, using beechwood xylan as a substrate, was 1916 U mg(-1). The xylanase activity was optimal at pH 5.0 and at 50 °C. In addition, the xynB was active over a pH range of 2.2 to 10.0. The apparent Km and Vmax values were 4.429 mg ml(-1) and 1429 U mg(-1), respectively.

Regulation of alcohol oxidase 1 (AOX1) promoter and peroxisome biogenesis in different fermentation processes in Pichia pastoris

Production of recombinant proteins is affected by process conditions, where transcriptional regulation of Pichia pastoris alcohol oxidase 1 (PpAOX1) promoter has been a key factor to influence expression levels of proteins of interest. Here, we demonstrate that the AOX1 promoter and peroxisome biogenesis are regulated based on different process conditions. Two types of GFP-fusion proteins, Ub-R-GFP (short-lived GFP in the cytosol) and GFP-SKL (peroxisomal targeting GFP), were successfully used to characterize the time-course of the AOX1 promoter and peroxisome biogenesis, respectively. The activity of the AOX1 promoter and peroxisome biogenesis was highly subjected to different fermentation process conditions - methanol-limited condition at normoxy (ML), switched feeding of carbon sources (e.g., glucose and methanol) under carbon-limited condition at normoxy (SML), and oxygen-limited (OL) condition. The AOX1 promoter was most active under the ML, but less active under the OL. Peroxisome biogenesis showed a high dependency on methanol consumption. In addition, the proliferation of peroxisomes was inhibited in a medium containing glucose and stimulated in the methanol phase under a carbon-limited fed-batch culture condition. The specific productivity of a monoclonal antibody (qp) under the AOX1 promoter was higher at 86h of induction in the ML than in the OL (0.026 vs 0.020mgg(-1)h(-1)). However, the oxygen-limited condition was a robust process suitable for longer induction (180h) due to high cell fitness. Our study suggests that the maximal production of a recombinant protein is highly dependent on methanol consumption rate that is affected by the availability of methanol and oxygen molecules.

Molecular cloning of a laccase gene from Ganoderma lucidum and heterologous expression in Pichia pastoris

A genomic laccase gene and cDNA were cloned from the white-rot fungi Ganoderma lucidum TR6. The genomic laccase gene contained 2086 bp with nine introns. The laccase cDNA had an open reading frame of 1563 bp. The deduced mature protein consisted of 520 amino acids. Both the genomic laccase gene and cDNA were expressed in the Pichia pastoris GS115. Laccase activities could be detected in transformants with laccase cDNA but not in transformants with genomic laccase gene. The highest activity value reached 685.8 U L(-1). The effects of temperature, pH and nitrogen source on laccase expression in P. pastoris were analyzed. The recombinant laccase was purified and the molecular mass was 73.4 KDa, a little bigger than native laccase. The optimal pH and temperature were specific at pH 3.5 and special range from 60 to 90 °C. The laccase was stable at pH 7.0 and temperature range of 20-30 °C. The Km and Vm values of this recombinant laccase for ABTS were 0.521 mM and 19.65 mM min(-1), respectively.

Recombinant expression of trypanosome surface glycoproteins in Pichia pastoris for the diagnosis of Trypanosoma evansi infection

Serodiagnosis of surra, which causes vast economic losses in livestock, is still based on native antigens purified from bloodstream form Trypanosoma (T.) evansi grown in rodents. To avoid the use of laboratory rodents in antigen preparation we expressed fragments of the invariant surface glycoprotein (ISG) 75, cloned from T. brucei gambiense cDNA, and the variant surface glycoprotein (VSG) RoTat 1.2, cloned from T. evansi gDNA, recombinantly in Pichia (P.) pastoris. The M5 strain of this yeast has an engineered N-glycosylation pathway resulting in homogenous Man5GlcNAc2 N-glycosylation which resembles the predominant Man9-5GlcNAc2 oligomannose structures in T. brucei. The secreted recombinant antigens were affinity purified with yields of up to 10mg and 20mg per liter cell culture of rISG 7529-465-E and rRoTat 1.223-385-H respectively. In ELISA, both recombinant proteins discriminated between pre-immune and immune serum samples of 25 goats experimentally infected with T. evansi. The diagnostic potential of rRoTat 1.223-385-H but not of rISG 7529-465-E was confirmed with sera of naturally infected and control dromedary camels. The results suggest that rRoTat 1.223-385-H expressed in P. pastoris requires further evaluation before it could replace native RoTat 1.2 VSG for serodiagnosis of surra, thus eliminating the use of laboratory animals for antigen production.

Further advances in the production of membrane proteins in Pichia pastoris

Membrane proteins have essential cellular functions and are therefore of high interest in both academia and industry. Many efforts have been made on producing those targets in yields allowing crystallization experiments aiming for high resolution structures and mechanistic understanding. The first step of production provides a crucial barrier to overcome, but what we now see, is great progress in membrane protein structural determination in a relatively short time. Achievements on recombinant protein production have been essential for this development and the yeast Pichia pastoris is the most commonly used host for eukaryotic membrane proteins. High-resolution structures nicely illustrate the successes in protein production, and this is the measure used by Ramón and Marin in their review "Advances in the production of membrane proteins in Pichia pastoris" from 2011. Here, additional advances on production and crystallization of eukaryotic membrane proteins are described and reflected on.

Cloning, expression and characterization of an ethanol tolerant GH3 β-glucosidase from Myceliophthora thermophila

The β-glucosidase gene bgl3a from Myceliophthora thermophila, member of the fungal glycosyl hydrolase (GH) family 3, was cloned and expressed in Pichia pastoris. The mature β-glucosidase gene, which results after the excision of one intron and the secreting signal peptide, was placed under the control of the strong alcohol oxidase promoter (AOX1) in the plasmid pPICZαC. The recombinant enzyme (90 kDa) was purified and characterized in order to evaluate its biotechnological potential. Recombinant P. pastoris efficiently secreted β-glucosidase into the medium and produced high level of enzymatic activity (41 U/ml) after 192 h of growth, under methanol induction. MtBgl3a was able to hydrolyze low molecular weight substrates and polysaccharides containing β-glucosidic residues. The K_m was found to be 0.39 mM on p-β-NPG and 2.64 mM on cellobiose. Optimal pH and temperature for the p-β-NPG hydrolysis were 5.0 and 70 °C. The β-glucosidase exhibits a half life of 143 min at 60 °C. Kinetic parameters of inhibition were determined for D-glucose, D-xylose and D-gluconic acid, indicating tolerance of the enzyme for these sugars and oxidized products. The recombinant enzyme was stimulated by short chain alcohols and has been shown to efficiently synthesize methyl-D-glucoside in the presence of methanol due to its transglycosylation activity. The stability of MtBgl3a in ethanol was prominent, and it retained most of its original activity after we exposed it to 50% ethanol for 6 h. The high catalytic performance, good thermal stability and tolerance to elevated concentrations of ethanol, D-xylose and D-glucose qualify this enzyme for use in the hydrolysis of lignocellulosic biomass for biofuel production, as part of an efficient complete multi-enzyme cocktail.

[Yeast-based production, purification and bioactivity assay of rainbow trout LECT2]

Leukocyte cell-derived chemotaxin 2 (LECT2) is a secretory cytokine that functions in many physiological and pathological processes. We used a Pichia pastoris expression system for the recombinant expression of rainbow trout LECT2. The recombinant LECT2 was purified by UNOsphere S Cation exchange and size-exclusion chromatography columns. The obtained target protein was highly pure (>96% homogeneity) and the yield was >120 mg/L of yeast cultures. An in vitro chamber assay revealed that recombinant LECT2 could induce chemotactic responses in rainbow trout head kidney-derived macrophages. Recombinant LECT2 not only enhanced macrophage respiratory burst activity and bactericidal activity, but also changed macrophage gene expression. In summary, we established a rapid and efficient method to prepare active recombinant rainbow trout LECT2 using a yeast expression system and column chromatography. Bioactive recombinant LECT2 is essential for studies on protein functions.

Potential combinatorial effects of recombinant atypical chemokine receptors in breast cancer cell invasion: A research perspective

Apart from their major function in the coordination of leukocyte recruitment, chemokines, in cooperation with their receptors, have been implicated in the progression of various diseases including different types of cancer, affecting survival, proliferation and metastasis. A complex network of chemokines and receptors exists in the tumor microenvironment and affects tumor development in various ways where chemokines activate typical signalling pathways by binding to the respective receptors. The identification and characterization of a group of atypical chemokine receptors [D6, Duffy antigen receptor for chemokines (DARC), ChemoCentryx chemokine receptor (CCX-CKR) and CXCR7] which appear to use unique biochemical properties to regulate the biological activities of these chemokines, is useful in the effort to therapeutically manipulate chemokines in a broad spectrum of diseases in which these chemokines play a critical role. The aim of this review was to investigate the combinatorial effect of two reported atypical chemokine receptors, D6 and DARC, on breast cancer cell invasion to understand their role and therapeutic potential in cancer treatment. In this regard, findings of the present review should be confirmed via the construction of recombinant D6 and DARC clones as well as the expression of the respective recombinant proteins using the Pichia pastoris (P. pastoris) expression system is to be performed in a future study in order to support findings of the current review.

Heterologous Expression of Phanerochaete chrysoporium Glyoxal Oxidase and its Application for the Coupled Reaction with Manganese Peroxidase to Decolorize Malachite Green

cDNA of the glx1 gene encoding glyoxal oxidase (GLX) from Phanerochaete chrysosporium was isolated and expressed in Pichia pastoris. The recombinant GLX (rGLX) produces H(2)O(2) over 7.0 nmol/min/mL using methyl glyoxal as a substrate. Use of rGLX as a generator of H(2)O(2) improved the coupled reaction with recombinant manganese peroxidase resulting in decolorization of malachite green up to 150 µM within 90 min.

Efficient expression systems for cysteine proteases of malaria parasites: too good to be true?

Papain-like cysteine proteases of malaria parasites are considered important chemotherapeutic targets or valuable models for the evaluation of drug candidates. Consequently, many of these enzymes have been cloned and expressed in Escherichia coli for their biochemical characterization. However, their expression has been problematic, showing low yield and leading to the formation of insoluble aggregates. Given that highly-productive expression systems are required for the high-throughput evaluation of inhibitors, we analyzed the existing expression systems to identify the causes of such apparent issues. We found that significant divergences in codon and nucleotide composition from host genes are the most probable cause of expression failure, and propose several strategies to overcome these limitations. Finally we predict that yeast hosts Saccharomyces cerevisiae and Pichia pastoris may be better suited than E. coli for the efficient expression of plasmodial genes, presumably leading to soluble and active products reproducing structural and functional characteristics of the natural enzymes.

A novel apoptosis correlated molecule: expression and characterization of protein Latcripin-1 from Lentinula edodes C(91-3)

An apoptosis correlated molecule—protein Latcripin-1 of Lentinula edodes C_91–3—was expressed and characterized in Pichia pastoris GS115. The total RNA was obtained from Lentinula edodes C_91–3. According to the transcriptome, the full-length gene of Latcripin-1 was isolated with 3′-Full Rapid Amplification of cDNA Ends (RACE) and 5′-Full RACE methods. The full-length gene was inserted into the secretory expression vector pPIC9K. The protein Latcripin-1 was expressed in Pichia pastoris GS115 and analyzed by Sodium Dodecylsulfonate Polyacrylate Gel Electrophoresis (SDS-PAGE) and Western blot. The Western blot showed that the protein was expressed successfully. The biological function of protein Latcripin-1 on A549 cells was studied with flow cytometry and the 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyl-tetrazolium Bromide (MTT) method. The toxic effect of protein Latcripin-1 was detected with the MTT method by co-culturing the characterized protein with chick embryo fibroblasts. The MTT assay results showed that there was a great difference between protein Latcripin-1 groups and the control group (p < 0.05). There was no toxic effect of the characterized protein on chick embryo fibroblasts. The flow cytometry showed that there was a significant difference between the protein groups of interest and the control group according to apoptosis function (p < 0.05). At the same time, cell ultrastructure observed by transmission electron microscopy supported the results of flow cytometry. The work demonstrates that protein Latcripin-1 can induce apoptosis of human lung cancer cells A549 and brings new insights into and advantages to finding anti-tumor proteins.

A comparative study on the expression, purification and functional characterization of human adiponectin in Pichia pastoris and Escherichia coli

Adiponectin is one of the most bioactive substances secreted by adipose tissue and is involved in the protection against metabolic syndrome, artherosclerosis and type II diabetes. Research into the use of adiponectin as a promising drug for metabolic syndromes requires production of this hormone in high quantities considering its molecular isoforms. The objective of this study is to produce recombinant human adiponectin by Pichia pastoris (P-ADP) as a cheap and convenient eukaryotic expression system for potential application in pharmaceutical therapy. For comparison, adiponectin was also expressed using the Escherichia coli (E-ADP) expression system. Adiponectin was constructed by overlap-extension PCR, and cloned in standard cloning vector and hosts. Recombinant expression vectors were cloned in the P. pastoris and E. coli host strains, respectively. SDS-PAGE and western blotting were used to detect and analyse expressed recombinant protein in both systems. Adiponectin was purified by affinity chromatography and quantified using the Bradford Assay. The results of this study indicated that P-ADP quantity (0.111 mg/mL) was higher than that of E-ADP (0.04 mg/mL) and both were produced in soluble form. However, P-ADP was able to form high molecular weights of adiponectin molecules, whilst E-ADP was not able to form isoforms higher than trimer. In addition, P-ADP was more active in lowering blood glucose compared with E-ADP. The two types of proteins were equally efficient and significantly decreased blood triglyceride and increased high density lipoprotein. We conclude that P. pastoris is able to produce high quantity of bioactive adiponectin for potential use in treatment of metabolic syndromes.

Expression and analysis of the glycosylation properties of recombinant human erythropoietin expressed in Pichia pastoris

The Pichia pastoris expression system was used to produce recombinant human erythropoietin, a protein synthesized by the adult kidney and responsible for the regulation of red blood cell production. The entire recombinant human erythropoietin (rhEPO) gene was constructed using the Splicing by Overlap Extension by PCR (SOE-PCR) technique, cloned and expressed through the secretory pathway of the Pichia expression system. Recombinant erythropoietin was successfully expressed in P. pastoris. The estimated molecular mass of the expressed protein ranged from 32 kDa to 75 kDa, with the variation in size being attributed to the presence of rhEPO glycosylation analogs. A crude functional analysis of the soluble proteins showed that all of the forms were active in vivo.

Heterologous Expression of Endo-1,4-beta-xylanaseA from Phanerochaete chrysosporium in Pichia pastoris

The cDNA of endo-1,4-β-xylanaseA, isolated from Phaenerocheate chrysosporium was expressed in Pichia pastoris. Using either the intrinsic leader peptide of XynA or the α-factor signal peptide of Saccharomyces cerevisiae, xylanaseA is efficiently secreted into the medium at maximum concentrations of 1,946 U/L and 2,496 U/L, respectively.

Reverse engineering of protein secretion by uncoupling of cell cycle phases from growth

The demand for recombinant proteins both for biopharmaceutical and technical applications is rapidly growing, and therefore the need to establish highly productive expression systems is steadily increasing. Yeasts, such as Pichia pastoris, are among the widely used production platforms with a strong emphasis on secreted proteins. Protein secretion is a limiting factor of productivity. There is strong evidence that secretion is coupled to specific growth rate (µ) in yeast, being higher at higher µ. For maximum productivity and product titer, high specific secretion rates at low µ would be desired. At high secretion rates cultures contain a large fraction of cells in the G2 and M phases of cell cycle. Consequently, the cell design target of a high fraction of cells in G2 + M phase was achieved by constitutive overexpression of the cyclin gene CLB2. Together with predictive process modeling this reverse engineered production strain improved the space time yield (STY) of an antibody Fab fragment by 18% and the product titer by 53%. This concept was verified with another secreted protein, human trypsinogen.

Expression of an endo-β-1,4-glucanase gene from orpinomyces PC-2 in Pichia pastoris

The endo-β-1,4-glucanase gene celE from the anaerobic fungus Orpinomyces PC-2 was placed under the control of an alcohol oxidase promoter (AOX1) in the plasmid pPIC9K, and integrated into the genome of a methylotrophic yeast P. pastoris GS115 by electroporation. The strain with highest endo-β-1,4-glucanase activity was selected and designed as P. pastoris egE, and cultivated in shaking flasks. The culture supernatant was assayed by SDS-polyacrylamide gel electrophoresis and showed a single band at about 52 kDa. Furthermore, the recombinant P. pastoris egE was proved to possess the ability to utilize sodium carboxymethyl cellulose as a carbon source. The recombinant endoglucanase produced by P. pastoris showed maximum activity at pH 6.0 and temperature 45 °C, indicating it was a mesophilic neutral endo-β-1,4-glucanase, suitable for denim biofinishing/washing. Further research was carried out in suitable fermentation medium in shaking flasks. The most favorable methanol addition concentration was discussed and given as 1.0%. After methanol induction for 96 h, the endo-β-1,4-glucanase activity reached 72.5 IU mL⁻¹. This is the first report on expression and characterization of endo-β-1,4-glucanase from Orpinomyces in P. pastoris. The endo-β-1,4-glucanase secreted by recombinant P. pastoris represents an attractive potential for both academic research and textile industry application.

Expression and Purification of Functionally Active Recombinant Human Alpha 1-Antitrypsin in Methylotrophic Yeast Pichia pastoris

Human alpha 1-antitrypsin (AAT) cDNA was obtained from HepG2 cell lines. After PCR and construction of expression vector pPICZα-AAT, human AAT was expressed in the yeast Pichia pastoris (P.pastoris) in a secretary manner and under the control of inducible alcohol oxidase 1 (AOX1) promoter. The amount of AAT protein in medium was measured as 60 mg/l 72 hr after induction with methanol. Results indicated the presence of protease inhibitory function of the protein against elastase. Purification was done using His-tag affinity chromatography. Due to the different patterns of glycosylation in yeast and human, the recombinant AAT showed different SDS-PAGE patterns compared to that of serum-derived AAT while pI shifted from 4.9 in native AAT compared to 5.2 in recombinant AAT constructed in this study.

Constitutive expression of Thermobifida fusca thermostable Acetylxylan Esterase gene in Pichia pastoris

A gene encoding the thermostable acetylxylan esterase (AXE) in Thermobifida fusca NTU22 was amplified by PCR, sequenced and cloned into the Pichia pastoris X-33 host strain using the vector pGAPZαA, allowing constitutive expression and secretion of the protein. Recombinant expression resulted in high levels of extracellular AXE production, as high as 526 U/mL in the Hinton flask culture broth. The purified enzyme showed a single band at about 28 kDa by SDS-polyacrylamide gel electrophoresis after being treated with endo-β-N-acetylglycosaminidase H; this agrees with the predicted size based on the nucleotide sequence. About 70% of the original activity remained after heat treatment at 60 °C for three hours. The optimal pH and temperature of the purified enzyme were 8.0 and 60 °C, respectively. The properties of the purified AXE from the P. pastoris transformant are similar to those of the AXE from an E. coli transformant.

Ribosome-inactivating proteins: from plant defense to tumor attack

Ribosome-inactivating proteins (RIPs) are EC3.2.32.22 N-glycosidases that recognize a universally conserved stem-loop structure in 23S/25S/28S rRNA, depurinating a single adenine (A4324 in rat) and irreversibly blocking protein translation, leading finally to cell death of intoxicated mammalian cells. Ricin, the plant RIP prototype that comprises a catalytic A subunit linked to a galactose-binding lectin B subunit to allow cell surface binding and toxin entry in most mammalian cells, shows a potency in the picomolar range. The most promising way to exploit plant RIPs as weapons against cancer cells is either by designing molecules in which the toxic domains are linked to selective tumor targeting domains or directly delivered as suicide genes for cancer gene therapy. Here, we will provide a comprehensive picture of plant RIPs and discuss successful designs and features of chimeric molecules having therapeutic potential.

Cloning and expression of Aspergillus tamarii FS132 lipase gene in Pichia pastoris

A lipase gene (atl) was cloned from Aspergillus tamarii FS132 for the first time. The gene was found to have an open reading frame of 1024 base pairs (bp), and the coding region of the gene contained two introns (51 bp and 52 bp). Multi-alignment analysis of the deduced amino acid sequence indicated high homology between the enzyme and mono-and diacylglycerol lipases from fungi Aspergillus. The recombinant lipase was expressed in Pichia pastoris GS115 cells. The recombinant lipase was found to have a molecular mass of 36.7 kDa, and it exhibited lipase activity of 20 U/mL in culture supernatant when tributyrin was used as the substrate.

Variable production windows for porcine trypsinogen employing synthetic inducible promoter variants in Pichia pastoris

Natural tools for recombinant protein production show technological limitations. Available natural promoters for gene expression in Pichia pastoris are either constitutive, weak or require the use of undesirable substances or procedures for induction. Here we show the application of deletion variants based on the well known methanol inducible AOX1 promoter and small synthetic promoters, where cis-acting elements were fused to core promoter fragments. They enable differently regulated target protein expression and at the same time to replace methanol induction by a glucose or glycerol feeding strategy. Trypsinogen, the precursor of the serine protease trypsin, was expressed using these different promoters. Depending on the applied promoter the production window (i.e. the time of increasing product concentration) changed significantly. In fedbatch processes trypsinogen yields before induction with methanol were up to 10 times higher if variants of the AOX1 promoter were applied. In addition, the starting point of autoproteolytic product degradation can be predetermined by the promoter choice.

High Expression of Methylotrophic Yeast-Derived Recombinant Human Erythropoietin in a pH-Controlled Batch System

To accomplish the worldwide demand for recombinant human erythropoietin (rHuEpo) as a therapeutic, application of cost-efficient expression system of methylotrophic yeast Pichia pastoris (P. pastoris) rather than mammalian cells is indispensable. Herein, a report on high levels secreted-expression of Pichia-derived rHuEpo by batch fermentation in a pH stabilized format is presented. The full length cDNA of rHuEpo was inserted into pPICZαA vector under control of AOX1 promoter, downstream of the secretion-α-factor and electroporated into P. pastoris strain X33. The highest expression transformant was selected by screening among the colonies surviving high concentration of Zeocin (1.0 mg/ml), followed by comparative small scale expression analysis by ELISA. Stabilization of pH around 6.0 by adding phosphoric acid into the culture media during induction period, improved the yield of expression to 150 mg/l of the media. Single-step Nickel-affinity chromatography was employed for purification of rHuEpo-6xHis to 80% purity. Analyses by SDS-PAGE, Western blot and N-terminal protein sequencing confirmed the authenticity of the 33 kDa expressed rHuEpo with a native N-terminal indicating the proper cleavage of secretion-signal. Results of this study, further confirmed the possibility of employing methylotrophic yeast for scaled up production aims of rHuEpo as a cost-efficient expression system when provided evidence for higher expression yields through application of pH-controlled systems.