Showing papers on "Pichia pastoris published in 1997"

Production of synthetic spider dragline silk protein in Pichia pastoris.

Abstract: The methylotrophic yeast Pichia pastoris was tested as a host for the production of long, repetitive protein polymers. Synthetic genes for a designed analog of a spider dragline silk protein were readily expressed at high levels under control of the methanol-inducible AOX1 promoter. Transformants containing multiple gene copies produced elevated levels of silk protein, but of a variety of altered sizes as a result of gene rearrangements at the time of transformation. Genes up to 3000 codons in length or longer could be expressed with no evidence of the prevalent truncated synthesis observed for similar genes in Escherichia coli, though genes longer than 1600 codons were expressed less efficiently than shorter genes. Silk-producing P. pastoris strains were stable without selection for at least 100 doublings.

A Recombinant Human Angiostatin Protein Inhibits Experimental Primary and Metastatic Cancer

Abstract: Endogenous murine angiostatin, identified as an internal fragment of plasminogen, blocks neovascularization and growth of experimental primary and metastatic tumors in vivo. A recombinant protein comprising kringles 1-4 of human plasminogen (amino acids 93-470) expressed in Pichia pastoris had physical properties (molecular size, binding to lysine, reactivity with antibody to kringles 1-3) that mimicked native angiostatin. This recombinant Angiostatin protein inhibited the proliferation of bovine capillary endothelial cells in vitro. Systemic administration of recombinant Angiostatin protein at doses of 1.5 mg/kg suppressed the growth of Lewis lung carcinoma-low metastatic phenotype metastases in C57BL/6 mice by greater than 90%; administration of the recombinant protein at doses of 100 mg/kg also suppressed the growth of primary Lewis lung carcinoma-low metastatic phenotype tumors. These findings demonstrate unambiguously that the antiangiogenic and antitumor activity of endogenous angiostatin resides within kringles 1-4 of plasminogen.

Assembly of human prolyl 4‐hydroxylase and type III collagen in the yeast Pichia pastoris: formation of a stable enzyme tetramer requires coexpression with collagen and assembly of a stable collagen requires coexpression with prolyl 4‐hydroxylase

Abstract: Prolyl 4-hydroxylase, the key enzyme of collagen synthesis, is an alpha2beta2 tetramer, the beta subunit of which is protein disulfide isomerase (PDI). Coexpression of the human alpha subunit and PDI in Pichia produced trace amounts of an active tetramer. A much higher, although still low, assembly level was obtained using a Saccharomyces pre-pro sequence in PDI. Coexpression with human type III procollagen unexpectedly increased the assembly level 10-fold, with no increase in the total amounts of the subunits. The recombinant enzyme was active not only in Pichia extracts but also inside the yeast cell, indicating that Pichia must have a system for transporting all the cosubstrates needed by the enzyme into the lumen of the endoplasmic reticulum. The 4-hydroxyproline-containing procollagen polypeptide chains were of full length and formed molecules with stable triple helices even though Pichia probably has no Hsp47-like protein. The data indicate that collagen synthesis in Pichia, and probably also in other cells, involves a highly unusual control mechanism, in that production of a stable prolyl 4-hydroxylase requires collagen expression while assembly of a stable collagen requires enzyme expression. This Pichia system seems ideal for the high-level production of various recombinant collagens for numerous scientific and medical purposes.

Improved tumour targeting by disulphide stabilized diabodies expressed in Pichia pastoris.

Abstract: Diabodies are dimeric antibody fragments held together by associated heavy and light chain variable domains present on different polypeptide chains. To improve their stability we have introduced cysteine residues into the V-domains to promote the disulphide crosslinking of the dimer. A crosslinked bivalent diabody against carcinoembryonic antigen (CEA) and a crosslinked bispecific diabody against CEA and the T-cell co-receptor CD3 were expressed from Pichia pastoris and Escherichia coli by secretion. From Pichia (but not E.coli) the chains were almost quantitatively crosslinked. Compared with the parent diabodies both crosslinked diabodies were more stable to heat (by >7 degrees C) and the crosslinked bivalent diabody showed improved localization to CEA+ human tumour xenografts in nude mice.

Laccase from the white-rot fungus Trametes versicolor : cDNA cloning of lcc1 and expression in Pichia pastoris

Abstract: A cDNA coding for laccase was isolated from the ligninolytic fungus Trametes versicolor by RNA-PCR. The cDNA corresponds to the gene lcc1, which encodes a laccase isoenzyme of 498 amino-acid residues preceded by a 22-residue signal peptide. The lcc1 cDNA was cloned into the vector pHIL-D2 for expression in Pichia pastoris under the control of the AOX1 promoter. Transformants were found to secrete active recombinant enzyme after induction with methanol. The use of growth medium buffered to pH 6.0 and control of pH during cultivation were found to be important, or even necessary, for obtaining activity in liquid cultures. The effect of exchanging the native secretion signal for the Saccharomyces cerevisiae α-factor pre-pro secretion signal was studied by cloning the portion encoding the mature enzyme into the vector pPIC9. The activity obtained for the construct encoding the native laccase signal sequence was found to be seven-fold higher than for the construct encoding the α-factor secretion signal. Utilisation of the P. pastoris pep4 mutant strain SMD1168 was found to provide a two-fold higher level of activity compared with P. pastoris GS115.

Total synthesis and functional overexpression of a candida rugosa lip1 gene coding for a major industrial lipase

Abstract: The dimorphic yeast Candida rugosa has an unusual codon-usage which hampers the functional expression of genes derived from this yeast in a conventional heterologous host. Lipases produced by this yeast are extensively used in industrial bioconversions, but commercial lipase samples contain several different isoforms encoded by the LIP genes family. In a first laborious attempt the LIP1 gene, encoding the major isoform of the C. rugosa lipases (CRLs), was systematically modified by site-directed mutagenesis to gain functional expression in S. cerevisiae. As alternative approach, the gene (1688 bp) was completely synthesised with an optimised nucleotide sequence in terms of heterologous expression in yeast and simplified genetic manipulation. The synthetic gene was functionally overexpressed in Pichia pastoris. The recombinant CRL was produced at high level and purity, accounting for 90-95 % of the secreted proteins. The physical-chemical and catalytic properties of the recombinant lipase were compared with those of a commercial, non-recombinant C. rugosa lipase preparation.

Cloning and disruption of the antigenic catalase gene of Aspergillus fumigatus.

Abstract: Aspergillus fumigatus possesses two catalases (described as fast and slow on the basis of their electrophoretic mobility). The slow catalase has been recognized as a diagnostic antigen for aspergillosis in immunocompetent patients. The antigenic catalase has been purified. The enzyme is a tetrameric protein composed of 90-kDa subunits. The corresponding cat1 gene was cloned, and sequencing data show that the cat1 gene codes for a 728-amino-acid polypeptide. A recombinant protein expressed in Pichia pastoris is enzymatically active and has biochemical and antigenic properties that are similar to those of the wild-type catalase. Molecular experiments reveal that CAT1 contains a signal peptide and a propeptide of 15 and 12 amino acid residues, respectively. cat1-disrupted mutants that were unable to produce the slow catalase were as sensitive to H2O2 and polymorphonuclear cells as the wild-type strain. In addition, there was no difference in pathogenicity between the cat1 mutant and its parental cat1+ strain in a murine model of aspergillosis.

Glucose-induced microautophagy in Pichia pastoris requires the alpha-subunit of phosphofructokinase.

Abstract: We have characterized biochemically, morphologically, and genetically two distinct pathways for the selective degradation of peroxisomes in Pichia pastoris. These pathways are independently regulated and analogous to microautophagy and macroautophagy that have been defined in mammalian cells. When P. pastoris is grown in methanol, cytosolic and peroxisomal enzymes necessary for methanol assimilation are synthesized. During adaptation from methanol to glucose, these enzymes are rapidly and selectively degraded within the yeast vacuole by microautophagy. We have isolated gsa mutants that are defective in glucose-induced selective autophagy of peroxisomes. In this study, we have shown that gsa1 is unable to sequester peroxisomes into the yeast vacuole. In addition, we provide evidence that the glucose-induced selective autophagy 1 (GSA1) protein is the alpha subunit of the phosphofructokinase enzyme complex encoded by PFK1. First, we can rescue the gsa1 mutant by transformation with a vector containing PFK1. Second, cellular levels of both PFK1 mRNA and phosphofructokinase activity are dramatically reduced in gsa1 when compared to the parental GS115. Third, a PFK1 knockout (delta pfk1) is unable to degrade alcohol oxidase during glucose adaptation. As observed in gsa1, the peroxisomes in delta pfk1 remain outside the vacuole during adaptation. Our data are consistent with the concept that PFK1 protein is required for an event upstream of vacuole degradation (i.e. signaling, selection, or sequestration). However, the degradation of peroxisomes does not require a catalytically active phosphofructokinase. The inability of delta pfk1 cells to degrade alcohol oxidase can be rescued by transformation with either normal PFK1 or mutant pfk1 whose catalytic site had been inactivated by a single amino acid mutation. We propose that PFK1 protein directly modulates glucose-induced microautophagy independent of its ability to metabolize glucose intermediates.

Peroxisomal multifunctional enzyme of beta-oxidation metabolizing D-3-hydroxyacyl-CoA esters in rat liver: molecular cloning, expression and characterization.

Abstract: In the present study we have cloned and characterized a novel rat peroxisomal multifunctional enzyme (MFE) named perMFE-II. The purified 2-enoyl-CoA hydratase 2 with an M(r) of 31500 from rat liver [Malila, Siivari, Makela, Jalonen, Latipaa, Kunau and Hiltunen (1993) J. Biol. Chem. 268, 21578-21585] was subjected to tryptic fragmentation and the resulting peptides were isolated and sequenced. Surprisingly, the full-length cDNA, amplified by PCR, had an open reading frame of 2205 bp encoding a polypeptide with a predicted M(r) of 79,331 and contained a potential peroxisomal targeting signal in the C-terminus (Ala-Lys-Leu). The sequenced peptide fragments of hydratase 2 gave a full match in the middle portion of the cDNA-derived amino acid sequence. The predicted amino acid sequence showed a high degree of similarity with pig 17 beta-hydroxysteroid dehydrogenase type IV and MFE of yeast peroxisomal beta-oxidation. Recombinant perMFE-II (produced in Pichia pastoris) had 2-enoyl-CoA hydratase 2 and D-specific 3-hydroxyacyl-CoA dehydrogenase activities and was catalytically active with several straight-chain trans-2-enoyl-CoA, 2-methyltetradecenoyl-CoA and pristenoyl-CoA esters. The results showed that in addition to an earlier described multifunctional isomerase-hydratase-dehydrogenase enzyme from rat liver peroxisomes (perMFE-I), another MFE exists in rat liver peroxisomes. They both catalyse sequential hydratase and dehydrogenase reactions of beta-oxidation but through reciprocal stereochemical courses.

Dipeptidyl-peptidase IV secreted by Aspergillus fumigatus, a fungus pathogenic to humans

Abstract: A dipeptidyl-peptidase IV was purified from the culture medium of the human-pathogenic fungus Aspergillus fumigatus. The enzyme has an apparent molecular mass of 95 kDa and contained approximately 10 kDa of N-linked carbohydrate. This glycoprotein is antigenic and has all characteristics of the class IV dipeptidyl-peptidases: removal of Xaa-Pro and to a lesser extent Xaa-Ala dipeptides from the N termini of peptides, including bioactive peptides such as neuropeptide Y, [des-Arg1] bradykinin, and glucagon-like peptide 1, activity at neutral pH, and presence in the amino acid sequence of the Gly-X-Ser-X-Gly consensus motif of the serine-hydrolases and the putative catalytic triad (Ser613, Asp690, His725) of the dipeptidyl-peptidases. Moreover, the last 200 amino acids displayed 60 to 65% similarity with the other dipeptidyl-peptidases IV from rat, mouse, human, and yeast. However, unlike the other dipeptidyl-peptidases, the dipeptidyl-peptidase IV of A. fumigatus is a secreted enzyme with a cleavable signal peptide. Expression of a recombinant dipeptidyl-peptidase IV of A. fumigatus has been attained in the yeast Pichia pastoris.

Protection of Mice Against a Lethal Influenza Challenge by Immunization with Yeast‐Derived Recombinant Influenza Neuraminidase

Abstract: The head domain of recombinant neuraminidase of A/Victoria/3/75 influenza virus was produced in a secreted form in the methylotrophic yeast Pichia pastoris using the P. pastoris alcohol oxidase 1 promoter and the Saccharomyces cerevisiae alpha-mating-factor signal sequence. Cultures in shake flasks provided expression levels of approximately 2.5-3 mg/l. Recombinant neuraminidase was purified from the culture medium to over 99% homogeneity. Although P. pastoris-secreted products are believed to carry shorter N-linked carbohydrate side chains than glycoproteins of S. cerevisiae, secreted neuraminidase was hyperglycosylated, with N-glycans of the high-mannose type containing up to 30-40 mannose residues. N-glycans were phosphorylated and only partially sensitive to alpha-mannosidase treatment. Balb/c mice immunized three times with 2 microg purified recombinant neuraminidase were 50% protected against a lethal challenge of mouse-adapted homologous virus; removal of glycosylation at the top of neuraminidase resulted in improved protection. The results provide a system for the production of an effective recombinant influenza vaccine that can easily be scaled up.

On-line monitoring and control of methanol concentration in shake-flask cultures of Pichia pastoris.

Abstract: The methylotrophic yeast Pichia pastoris can be used to express recombinant genes at high levels under the control of the methanol-inducible alcohol oxidase 1 (AOX1) promoter. Accurate regulation of the methanol concentration in P. pastoris cultures is necessary to maintain induction, while preventing accumulation of methanol to cytotoxic levels. We developed an inexpensive methanol sensor that uses a gas-permeable silicone rubber tube immersed in the culture medium and an organic solvent vapor detector. The sensor was used to monitor methanol concentration continuously throughout a fed-batch shake-flask culture of a P. pastoris clone producing the N-lobe of human transferrin. The sensor calibration was stable for the duration of the culture and the output signal accurately reflected the methanol concentration determined off-line by HPLC. A closed-loop control system utilizing this sensor was developed and used to maintain a 0.3% (v/v) methanol concentration in the culture. Use of this system resulted in a fivefold increase in volumetric protein productivity over levels obtained using the conventional fed-batch protocol.

Expression of the dengue virus structural proteins in Pichia pastoris leads to the generation of virus-like particles.

Abstract: We have expressed cDNA encoding the dengue virus structural proteins in Pichia pastoris by chromosomal integration of an expression cassette containing the dengue virus structural genes (CprME). The yeast recombinant E protein migrated during SDS-PAGE as a 65 kDa protein when analysed by Western blotting and radioimmunoprecipitation, which is the expected molecular mass for correctly processed and glycosylated E protein. Treatment with endoglycosidases showed that the recombinant E protein was modified by the addition of short mannose chains. The E protein migrated with a buoyant density of 1.13 g/cm3 when analysed using sucrose density gradient centrifugation. Spherical structures with an average diameter of 30 nm, whose morphology resembles dengue virions, were observed in the purified fractions using transmission electron microscopy. Furthermore, the virus-like particles were immunogenic in animals and were able to induce neutralizing antibodies. This is the first report that expression of the structural genes of a flavivirus in yeast is able to generate particulate structures that resemble virions.

High-level expression of bovine beta-lactoglobulin in Pichia pastoris and characterization of its physical properties

Abstract: Bovine beta-lactoglobulin (BLG) variant A has been expressed in the methylotropic yeast Pichia pastoris by fusion of the cDNA to the sequence coding for the alpha-mating factor prepro-leader peptide from Saccharomyces cerevisiae. P. pastoris Mut+ transformants were obtained by single cross-over integration of the BLG-containing vector into the AOX1 locus. In a fed-batch fermenter, a cell density of approximately 300 mg/ml was achieved by controlled glycerol feeding for a total of 24 h. After 72 h of methanol induction, the secreted BLG reached levels of > 1 g/l. The secreted protein could be purified to homogeneity by ion-exchange chromatography. Amino-terminal sequencing of the secreted BLG revealed that the Glu-Ala spacer repeats inserted between the mature protein and the alpha-factor prepro-leader were still present. The purified protein was characterized by a number of methods, including CD spectroscopy, guanidine-HCl unfolding, crystallization and two-dimensional 1H-NMR spectroscopy. By all of these measures, the physical characteristics of recombinant BLG were indistinguishable from those of the native purified bovine BLG, making it useful as a model for protein folding and other biophysical studies.

Biosynthetic production of type II fish antifreeze protein: fermentation by Pichia pastoris

Abstract: Sea raven type II antifreeze protein (SRAFP) is one of three diAerent fish antifreeze proteins isolated to date. These proteins are known to bind to the surface of ice and inhibit its growth. To solve the three-dimen- sional structure of SRAFP, study its ice-binding mech- anism, and as a basis for engineering these molecules, an eAcient system for its biosynthetic production was de- veloped. Several diAerent expression systems have been tested including baculovirus, Escherichia coli and yeast. The latter, using the methylotrophic organism Pichia pastoris as the host, was the most productive. In shake- flask cultures the levels of SRAFP secreted from Pichia were up to 5 mg/l. The recombinant protein has an identical activity to SRAFP from sea raven serum. In order to increase yields further, four diAerent strate- gies were tested in 10-l fermentation vessels, including: (1) optimization of pH and dissolved oxygen, (2) mixed feeding of methanol and glycerol with Mut s clones, (3) supplementation of amino acid building blocks, and (4) methanol feeding with Mut + clones. The mixed- feeding/Mut s strategy proved to be the most eAcient with SRAFP yields reaching 30 mg/l.

Peroxisomal Targeting, Import, and Assembly of Alcohol Oxidase in Pichia pastoris

Abstract: Alcohol oxidase (AOX), the first enzyme in the yeast methanol utilization pathway is a homooctameric peroxisomal matrix protein. In peroxisome biogenesis-defective (pex) mutants of the yeast Pichia pastoris, AOX fails to assemble into active octamers and instead forms inactive cytoplasmic aggregates. The apparent inability of AOX to assemble in the cytoplasm contrasts with other peroxisomal proteins that are able to oligomerize before import. To further investigate the import of AOX, we first identified its peroxisomal targeting signal (PTS). We found that sequences essential for targeting AOX are primarily located within the four COOH-terminal amino acids of the protein leucine-alanine-arginine-phenylalanine COOH (LARF). To examine whether AOX can oligomerize before import, we coexpressed AOX without its PTS along with wild-type AOX and determined whether the mutant AOX could be coimported into peroxisomes. To identify the mutant form of AOX, the COOH-terminal LARF sequence of the protein was replaced with a hemagglutinin epitope tag (AOX-HA). Coexpression of AOX-HA with wild-type AOX (AOX-WT) did not result in an increase in the proportion of AOX-HA present in octameric active AOX, suggesting that newly synthesized AOX-HA cannot oligomerize with AOX-WT in the cytoplasm. Thus, AOX cannot initiate oligomerization in the cytoplasm, but must first be targeted to the organelle before assembly begins.

Recombinant HMG1 Protein Produced in Pichia pastoris: A Nonviral Gene Delivery Agent

Abstract: This paper describes the production of a recombinant protein from the expression system based on the methylotrophic yeast Pichia pastoris. Efficient production of rat high-mobility-group 1 (HMG1) protein was obtained using the system. Two forms of HMG1 were secreted into the culture medium: a 24.5-kDa species corresponding to the native HMG1 and a 32-kDa glycosylated derivative. Non-glycosylated recombinant HMG1 was purified easily and shown to possess the same DNA-binding properties as HMG1 purified from calf thymus. Plasmid DNA complexed to the recombinant HMG1 is taken up by a variety of mammalian cells in culture. Transient expression of a luciferase reporter gene was observed. Under selective conditions, stable expression of a neomycin gene was established as a result of integration into the genome. HMG1-mediated gene delivery was as efficient as calcium phosphate-mediated transfection but without associated cell damage. In addition, stable transfectants obtained after selection for G418 resistance usually integrated only one copy of the transfected DNA in contrast to the high unpredictable number obtained by the calcium phosphate method. HMG1 transfection complexes were not toxic to cultured cells, even at high concentrations.