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Jin FJ, Hu S, Wang BT, Jin L. Advances in Genetic Engineering Technology and Its Application in the Industrial Fungus Aspergillus oryzae. Front Microbiol 2021; 12:644404. [PMID: 33708187 PMCID: PMC7940364 DOI: 10.3389/fmicb.2021.644404] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 02/05/2021] [Indexed: 12/19/2022] Open
Abstract
The filamentous fungus Aspergillus oryzae is an important strain in the traditional fermentation and food processing industries and is often used in the production of soy sauce, soybean paste, and liquor-making. In addition, A. oryzae has a strong capacity to secrete large amounts of hydrolytic enzymes; therefore, it has also been used in the enzyme industry as a cell factory for the production of numerous native and heterologous enzymes. However, the production and secretion of foreign proteins by A. oryzae are often limited by numerous bottlenecks that occur during transcription, translation, protein folding, translocation, degradation, transport, secretion, etc. The existence of these problems makes it difficult to achieve the desired target in the production of foreign proteins by A. oryzae. In recent years, with the decipherment of the whole genome sequence, basic research and genetic engineering technologies related to the production and utilization of A. oryzae have been well developed, such as the improvement of homologous recombination efficiency, application of selectable marker genes, development of large chromosome deletion technology, utilization of hyphal fusion techniques, and application of CRISPR/Cas9 genome editing systems. The development and establishment of these genetic engineering technologies provided a great deal of technical support for the industrial production and application of A. oryzae. This paper reviews the advances in basic research and genetic engineering technologies of the fermentation strain A. oryzae mentioned above to open up more effective ways and research space for the breeding of A. oryzae production strains in the future.
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Affiliation(s)
- Feng-Jie Jin
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, China
| | - Shuang Hu
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, China
| | - Bao-Teng Wang
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, China
| | - Long Jin
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, China
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Abstract
Aspergilli have been widely used in the production of organic acids, enzymes, and secondary metabolites for almost a century. Today, several GRAS (generally recognized as safe) Aspergillus species hold a central role in the field of industrial biotechnology with multiple profitable applications. Since the 1990s, research has focused on the use of Aspergillus species in the development of cell factories for the production of recombinant proteins mainly due to their natively high secretion capacity. Advances in the Aspergillus-specific molecular toolkit and combination of several engineering strategies (e.g., protease-deficient strains and fusions to carrier proteins) resulted in strains able to generate high titers of recombinant fungal proteins. However, the production of non-fungal proteins appears to still be inefficient due to bottlenecks in fungal expression and secretion machinery. After a brief overview of the different heterologous expression systems currently available, this review focuses on the filamentous fungi belonging to the genus Aspergillus and their use in recombinant protein production. We describe key steps in protein synthesis and secretion that may limit production efficiency in Aspergillus systems and present genetic engineering approaches and bioprocessing strategies that have been adopted in order to improve recombinant protein titers and expand the potential of Aspergilli as competitive production platforms.
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Nevalainen H, Peterson R, Curach N. Overview of Gene Expression Using Filamentous Fungi. ACTA ACUST UNITED AC 2019; 92:e55. [PMID: 30040195 DOI: 10.1002/cpps.55] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Filamentous fungi are lower eukaryotes increasingly used for expression of foreign proteins ranging from industrial enzymes originating from other fungi and bacteria to proteins of mammalian origin, such as antibodies and growth factors. Their strengths include an excellent capacity for protein secretion and their eukaryotic protein processing machinery. Proteins secreted from filamentous fungi are modified in the secretory pathway, with folding, proteolytic processing, and addition of glycans being the main modifications. Unlike from many other expression systems, however, plasmids and host strains for expression of gene products in filamentous fungi are not readily available commercially, and the expression system must thus be stitched together in the laboratory. In this overview, the key elements of fungal expression systems are discussed from a practical point of view and with a view towards the future. The principles and considerations presented here can be applied to a range of filamentous fungi. © 2018 by John Wiley & Sons, Inc.
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Affiliation(s)
- Helena Nevalainen
- Department of Molecular Sciences, Macquarie University, Sydney, Australia.,Biomolecular Discovery and Design Research Centre, Macquarie University, Sydney, Australia
| | - Robyn Peterson
- Department of Molecular Sciences, Macquarie University, Sydney, Australia.,Biomolecular Discovery and Design Research Centre, Macquarie University, Sydney, Australia
| | - Natalie Curach
- Department of Molecular Sciences, Macquarie University, Sydney, Australia
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Heimel K. Unfolded protein response in filamentous fungi-implications in biotechnology. Appl Microbiol Biotechnol 2014; 99:121-32. [PMID: 25384707 DOI: 10.1007/s00253-014-6192-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 10/24/2014] [Accepted: 10/27/2014] [Indexed: 01/16/2023]
Abstract
The unfolded protein response (UPR) represents a mechanism to preserve endoplasmic reticulum (ER) homeostasis that is conserved in eukaryotes. ER stress caused by the accumulation of potentially toxic un- or misfolded proteins in the ER triggers UPR activation and the induction of genes important for protein folding in the ER, ER expansion, and transport from and to the ER. Along with this adaptation, the overall capacity for protein secretion is markedly increased by the UPR. In filamentous fungi, various approaches to employ the UPR for improved production of homologous and heterologous proteins have been investigated. As the effects on protein production were strongly dependent on the expressed protein, generally applicable strategies have to be developed. A combination of transcriptomic approaches monitoring secretion stress and basic research on the UPR mechanism provided novel and important insight into the complex regulatory cross-connections between UPR signalling, cellular physiology, and developmental processes. It will be discussed how this increasing knowledge on the UPR might stimulate the development of novel strategies for using the UPR as a tool in biotechnology.
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Affiliation(s)
- Kai Heimel
- Institut für Mikrobiologie & Genetik, Georg-August-Universität, Grisebachstr. 8, 37077, Göttingen, Germany,
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Malavazi I, Goldman GH, Brown NA. The importance of connections between the cell wall integrity pathway and the unfolded protein response in filamentous fungi. Brief Funct Genomics 2014; 13:456-70. [PMID: 25060881 DOI: 10.1093/bfgp/elu027] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In the external environment, or within a host organism, filamentous fungi experience sudden changes in nutrient availability, osmolality, pH, temperature and the exposure to toxic compounds. The fungal cell wall represents the first line of defense, while also performing essential roles in morphology, development and virulence. A polarized secretion system is paramount for cell wall biosynthesis, filamentous growth, nutrient acquisition and interactions with the environment. The unique ability of filamentous fungi to secrete has resulted in their industrial adoption as fungal cell factories. Protein maturation and secretion commences in the endoplasmic reticulum (ER). The unfolded protein response (UPR) maintains ER functionality during exposure to secretion and cell wall stress. UPR, therefore, influences secretion and cell wall homeostasis, which in turn impacts upon numerous fungal traits important to pathogenesis and biotechnology. Subsequently, this review describes the relevance of the cell wall and UPR systems to filamentous fungal pathogens or industrial microbes and then highlights interconnections between the two systems. Ultimately, the possible biotechnological applications of an enhanced understanding of such regulatory systems in combating fungal disease, or the removal of natural bottlenecks in protein secretion in an industrial setting, are discussed.
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Molecular characterization and analysis of a novel protein disulfide isomerase-like protein of Eimeria tenella. PLoS One 2014; 9:e99914. [PMID: 24932912 PMCID: PMC4059736 DOI: 10.1371/journal.pone.0099914] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 05/19/2014] [Indexed: 12/13/2022] Open
Abstract
Protein disulfide isomerase (PDI) and PDI-like proteins are members of the thioredoxin superfamily. They contain thioredoxin-like domains and catalyze the physiological oxidation, reduction and isomerization of protein disulfide bonds, which are involved in cell function and development in prokaryotes and eukaryotes. In this study, EtPDIL, a novel PDI-like gene of Eimeria tenella, was cloned using rapid amplification of cDNA ends (RACE) according to the expressed sequence tag (EST). The EtPDIL cDNA contained 1129 nucleotides encoding 216 amino acids. The deduced EtPDIL protein belonged to thioredoxin-like superfamily and had a single predicted thioredoxin domain with a non-classical thioredoxin-like motif (SXXC). BLAST analysis showed that the EtPDIL protein was 55–59% identical to PDI-like proteins of other apicomplexan parasites. The transcript and protein levels of EtPDIL at different development stages were investigated by real-time quantitative PCR and western blot. The messenger RNA and protein levels of EtPDIL were higher in sporulated oocysts than in unsporulated oocysts, sporozoites or merozoites. Protein expression was barely detectable in unsporulated oocysts. Western blots showed that rabbit antiserum against recombinant EtPDIL recognized only a native 24 kDa protein from parasites. Immunolocalization with EtPDIL antibody showed that EtPDIL had a disperse distribution in the cytoplasm of whole sporozoites and merozoites. After sporozoites were incubated in complete medium, EtPDIL protein concentrated at the anterior of the sporozoites and appeared on the surface of parasites. Specific staining was more intense and mainly located on the parasite surface after merozoites released from mature schizonts invaded DF-1 cells. After development of parasites in DF-1 cells, staining intensified in trophozoites, immature schizonts and mature schizonts. Antibody inhibition of EtPDIL function reduced the ability of E. tenella to invade DF-1 cells. These results suggested that EtPDIL might be involved in sporulation in external environments and in host cell adhesion, invasion and development of E. tenella.
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Nevalainen H, Peterson R. Making recombinant proteins in filamentous fungi- are we expecting too much? Front Microbiol 2014; 5:75. [PMID: 24578701 PMCID: PMC3936196 DOI: 10.3389/fmicb.2014.00075] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Accepted: 02/11/2014] [Indexed: 11/13/2022] Open
Abstract
Hosts used for the production of recombinant proteins are typically high-protein secreting mutant strains that have been selected for a specific purpose, such as efficient production of cellulose-degrading enzymes. Somewhat surprisingly, sequencing of the genomes of a series of mutant strains of the cellulolytic Trichoderma reesei, widely used as an expression host for recombinant gene products, has shed very little light on the nature of changes that boost high-level protein secretion. While it is generally agreed and shown that protein secretion in filamentous fungi occurs mainly through the hyphal tip, there is growing evidence that secretion of proteins also takes place in sub-apical regions. Attempts to increase correct folding and thereby the yields of heterologous proteins in fungal hosts by co-expression of cellular chaperones and foldases have resulted in variable success; underlying reasons have been explored mainly at the transcriptional level. The observed physiological changes in fungal strains experiencing increasing stress through protein overexpression under strong gene promoters also reflect the challenge the host organisms are experiencing. It is evident, that as with other eukaryotes, fungal endoplasmic reticulum is a highly dynamic structure. Considering the above, there is an emerging body of work exploring the use of weaker expression promoters to avoid undue stress. Filamentous fungi have been hailed as candidates for the production of pharmaceutically relevant proteins for therapeutic use. One of the biggest challenges in terms of fungally produced heterologous gene products is their mode of glycosylation; fungi lack the functionally important terminal sialylation of the glycans that occurs in mammalian cells. Finally, exploration of the metabolic pathways and fluxes together with the development of sophisticated fermentation protocols may result in new strategies to produce recombinant proteins in filamentous fungi.
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Affiliation(s)
- Helena Nevalainen
- Biomolecular Frontiers Research Centre, Department of Chemistry and Biomolecular Sciences, Macquarie University, SydneyNSW, Australia
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Ohno A, Maruyama JI, Nemoto T, Arioka M, Kitamoto K. A carrier fusion significantly induces unfolded protein response in heterologous protein production by Aspergillus oryzae. Appl Microbiol Biotechnol 2011; 92:1197-206. [PMID: 21822643 DOI: 10.1007/s00253-011-3487-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 07/14/2011] [Indexed: 11/26/2022]
Abstract
In heterologous protein production by filamentous fungi, target proteins are expressed as fusions with homologous secretory proteins, called carriers, for higher production yields. Although carrier fusion is thought to overcome the bottleneck in transcriptional and (post)translational processes during heterologous protein production, there is limited knowledge of its physiological effects on the host strain. In this study, we performed DNA microarray analysis by comparing gene expression patterns of two Aspergillus oryzae strains expressing either carrier- or non-carrier-fused bovine chymosin (CHY). When CHY was expressed as a fusion with α-amylase (AmyB), the production level increased by approximately 2-fold as compared with the non-carrier-fused CHY. DNA microarray analysis revealed that the carrier fusion significantly up-regulated many genes involved in endoplasmic reticulum (ER) protein-folding and secretion. Consistently, hacA transcripts were efficiently spliced in the strain expressing the carrier-fused CHY, indicating an unfolded protein response (UPR). The carrier-fused CHY was detected intracellularly without processing at the Kex2 cleavage site, which is likely recognized in the Golgi, and the carrier fusion delayed extracellular CHY production in the early growth phase as compared with the non-carrier-fused expression. Taken together, our data suggest a proposal that the carrier fusion temporarily accumulates the carrier-fused CHY in the ER and significantly induces UPR.
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Affiliation(s)
- Ayako Ohno
- Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Japan
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Approaches for refining heterologous protein production in filamentous fungi. World J Microbiol Biotechnol 2009. [DOI: 10.1007/s11274-009-0128-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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10
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Nowrousian M, Frank S, Koers S, Strauch P, Weitner T, Ringelberg C, Dunlap JC, Loros JJ, Kück U. The novel ER membrane protein PRO41 is essential for sexual development in the filamentous fungus Sordaria macrospora. Mol Microbiol 2007; 64:923-37. [PMID: 17501918 PMCID: PMC3694341 DOI: 10.1111/j.1365-2958.2007.05694.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The filamentous fungus Sordaria macrospora develops complex fruiting bodies (perithecia) to propagate its sexual spores. Here, we present an analysis of the sterile mutant pro41 that is unable to produce mature fruiting bodies. The mutant carries a deletion of 4 kb and is complemented by the pro41 open reading frame that is contained within the region deleted in the mutant. In silico analyses predict PRO41 to be an endoplasmic reticulum (ER) membrane protein, and a PRO41-EGFP fusion protein colocalizes with ER-targeted DsRED. Furthermore, Western blot analysis shows that the PRO41-EGFP fusion protein is present in the membrane fraction. A fusion of the predicted N-terminal signal sequence of PRO41 with EGFP is secreted out of the cell, indicating that the signal sequence is functional. pro41 transcript levels are upregulated during sexual development. This increase in transcript levels was not observed in the sterile mutant pro1 that lacks a transcription factor gene. Moreover, microarray analysis of gene expression in the mutants pro1, pro41 and the pro1/41 double mutant showed that pro41 is partly epistatic to pro1. Taken together, these data show that PRO41 is a novel ER membrane protein essential for fruiting body formation in filamentous fungi.
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Affiliation(s)
- Minou Nowrousian
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Bochum, Germany
| | - Sandra Frank
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Bochum, Germany
| | - Sandra Koers
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Bochum, Germany
| | - Peter Strauch
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Bochum, Germany
| | - Thomas Weitner
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Bochum, Germany
| | - Carol Ringelberg
- Departments of Genetics and Biochemistry, Dartmouth Medical School, Hanover, NH, USA
| | - Jay C. Dunlap
- Departments of Genetics and Biochemistry, Dartmouth Medical School, Hanover, NH, USA
| | - Jennifer J. Loros
- Departments of Genetics and Biochemistry, Dartmouth Medical School, Hanover, NH, USA
| | - Ulrich Kück
- Departments of Genetics and Biochemistry, Dartmouth Medical School, Hanover, NH, USA
- For correspondence. ; Tel. (+49) 0 234 3226212; Fax (+49) 0 234 3214184
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Genomic analysis of the secretion stress response in the enzyme-producing cell factory Aspergillus niger. BMC Genomics 2007; 8:158. [PMID: 17561995 PMCID: PMC1894978 DOI: 10.1186/1471-2164-8-158] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Accepted: 06/11/2007] [Indexed: 11/29/2022] Open
Abstract
Background Filamentous fungi such as Aspergillus niger have a high capacity secretory system and are therefore widely exploited for the industrial production of native and heterologous proteins. However, in most cases the yields of non-fungal proteins are significantly lower than those obtained for fungal proteins. One well-studied bottleneck appears to be the result of mis-folding of heterologous proteins in the ER during early stages of secretion, with related stress responses in the host, including the unfolded protein response (UPR). This study aims at uncovering transcriptional and translational responses occurring in A. niger exposed to secretion stress. Results A genome-wide transcriptional analysis of protein secretion-related stress responses was determined using Affymetrix DNA GeneChips and independent verification for selected genes. Endoplasmic reticulum (ER)-associated stress was induced either by chemical treatment of the wild-type cells with dithiothreitol (DTT) or tunicamycin, or by expressing a human protein, tissue plasminogen activator (t-PA). All of these treatments triggered the UPR, as shown by the expression levels of several well-known UPR target genes. The predicted proteins encoded by most of the up-regulated genes function as part of the secretory system including chaperones, foldases, glycosylation enzymes, vesicle transport proteins, and ER-associated degradation proteins. Several genes were down-regulated under stress conditions and these included several genes that encode secreted enzymes. Moreover, translational regulation under ER stress was investigated by polysomal fractionation. This analysis confirmed the post-transcriptional control of hacA expression and highlighted that differential translation also occurs during ER stress, in particular for some genes encoding secreted proteins or proteins involved in ribosomal biogenesis and assembly. Conclusion This is first genome-wide analysis of both transcriptional and translational events following protein secretion stress. Insight has been gained into the molecular basis of protein secretion and secretion-related stress in an effective protein-secreting fungus, and provides an opportunity to identify target genes for manipulation in strain improvement strategies.
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Mulder HJ, Nikolaev I, Madrid SM. HACA, the transcriptional activator of the unfolded protein response (UPR) in Aspergillus niger, binds to partly palindromic UPR elements of the consensus sequence 5'-CAN(G/A)NTGT/GCCT-3'. Fungal Genet Biol 2006; 43:560-72. [PMID: 16709461 DOI: 10.1016/j.fgb.2006.02.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2005] [Revised: 02/10/2006] [Accepted: 02/16/2006] [Indexed: 11/29/2022]
Abstract
The promoters of UPR target genes contain an unfolded protein response element (UPRE), which confers the stress inducibility to the gene, via an interaction with the transcription activator HACA. In the promoters of the Aspergillus ER-stress responsive genes bipA, cypB, pdiA, prpA, tigA, and hacA, a consensus sequence was identified, which was located close to the transcription start site of the gene (<81 bp), and corresponds to the sequence CAN(G/A)NTGT/GCCT. The UPRE is a partly palindromic sequence around a dispensable spacer nucleotide, followed by four highly conserved bases. By an in vitro selection procedure, an optimal binding site for HACA was isolated. This sequence, ACACGTGTCCT, resembles the UPRE but lacks the spacer nucleotide. It has a much higher binding affinity than the identified UPREs, and in vivo it behaves as a more powerful cis-acting element.
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Affiliation(s)
- Harm J Mulder
- Danisco Innovation Copenhagen, Langebrogade 1, DK 1001 Copenhagen, Denmark.
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Liang Y, Li W, Ma Q, Zhang Y. Functional analysis of tunicamycin-inducible gene A polypeptide from Aspergillus niger. Biochem Cell Biol 2005; 83:654-8. [PMID: 16234854 DOI: 10.1139/o05-117] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Tunicamycin-inducible gene A polypeptide (TIGA) is a member of the protein disulfide isomerase (PDI) family and is suggested to facilitate the folding of nascent polypeptides. The functional properties of TIGA were investigated here. TIGA acted as an isomerase, catalyzing the refolding of denatured and reduced ribonuclease A. TIGA also exhibited chaperone activity in the refolding of denatured prochymosin but not in the refolding of glyceraldehyde 3-phosphate dehydrogenase (GAPDH), indicating that it had substrate specificity with respect to chaperone activity. Detailed study with a series of thioredoxin-motif (trx-motif) mutants revealed that the 2 trx-motifs of TIGA were not equal in activity. The N-terminal trx-motif was more active than the C-terminal trx-motif, and the first cysteine in each trx-motif was necessary for isomerase activity.
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Affiliation(s)
- Yurong Liang
- Institute ofMicrobiology, Chinese Academy of Sciences, Beijing 100080,China
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Nevalainen KMH, Te'o VSJ, Bergquist PL. Heterologous protein expression in filamentous fungi. Trends Biotechnol 2005; 23:468-74. [PMID: 15967521 DOI: 10.1016/j.tibtech.2005.06.002] [Citation(s) in RCA: 172] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2005] [Revised: 05/06/2005] [Accepted: 06/07/2005] [Indexed: 10/25/2022]
Abstract
Filamentous fungi are commonly used in the fermentation industry for the large-scale production of proteins--mainly industrial enzymes. Recent advances in fungal genomics and related experimental technologies such as gene arrays and proteomics are rapidly changing the approaches to the development and use of filamentous fungi as hosts for the production of both homologous and heterologous gene products. The emphasis is moving towards sourcing new genes of interest through database mining and unravelling the circuits related to fungal gene regulation, applying, for example, transcriptomics. However, although heterologous fungal proteins are efficiently expressed, expression of gene products from other organisms is subject to several bottlenecks that reduce yield. Current approaches emphasize the study of pathways involved in protein modification and degradation in general rather than gene-by-gene approaches.
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Affiliation(s)
- K M Helena Nevalainen
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney NSW 2109, Australia.
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15
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Geysens S, Pakula T, Uusitalo J, Dewerte I, Penttilä M, Contreras R. Cloning and characterization of the glucosidase II alpha subunit gene of Trichoderma reesei: a frameshift mutation results in the aberrant glycosylation profile of the hypercellulolytic strain Rut-C30. Appl Environ Microbiol 2005; 71:2910-24. [PMID: 15932985 PMCID: PMC1151825 DOI: 10.1128/aem.71.6.2910-2924.2005] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We describe isolation and characterization of the gene encoding the glucosidase II alpha subunit (GIIalpha) of the industrially important fungus Trichoderma reesei. This subunit is the catalytic part of the glucosidase II heterodimeric enzyme involved in the structural modification within the endoplasmic reticulum (ER) of N-linked oligosaccharides present on glycoproteins. The gene encoding GIIalpha (gls2alpha) in the hypercellulolytic strain Rut-C30 contains a frameshift mutation resulting in a truncated gene product. Based on the peculiar monoglucosylated N-glycan pattern on proteins produced by the strain, we concluded that the truncated protein can still hydrolyze the first alpha-1,3-linked glucose residue but not the innermost alpha-1,3-linked glucose residue from the Glc2Man9GlcNAc2 N-glycan ER structure. Transformation of the Rut-C30 strain with a repaired T. reesei gls2alpha gene changed the glycosylation profile significantly, decreasing the amount of monoglucosylated structures and increasing the amount of high-mannose N-glycans. Full conversion to high-mannose carbohydrates was not obtained, and this was probably due to competition between the endogenous mutant subunit and the introduced wild-type GIIalpha protein. Since glucosidase II is also involved in the ER quality control of nascent polypeptide chains, its transcriptional regulation was studied in a strain producing recombinant tissue plasminogen activator (tPA) and in cultures treated with the stress agents dithiothreitol (DTT) and brefeldin A (BFA), which are known to block protein transport and to induce the unfolded protein response. While the mRNA levels were clearly upregulated upon tPA production or BFA treatment, no such enhancement was observed after DTT addition.
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Affiliation(s)
- Steven Geysens
- Fundamental and Applied Molecular Biology, Department for Molecular Biomedical Research, Ghent University and VIB (Flemish Interuniversity Institute for Biotechnology), Ghent-Zwijnaarde, Belgium
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Sims AH, Gent ME, Lanthaler K, Dunn-Coleman NS, Oliver SG, Robson GD. Transcriptome analysis of recombinant protein secretion by Aspergillus nidulans and the unfolded-protein response in vivo. Appl Environ Microbiol 2005; 71:2737-47. [PMID: 15870366 PMCID: PMC1087583 DOI: 10.1128/aem.71.5.2737-2747.2005] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Filamentous fungi have a high capacity for producing large amounts of secreted proteins, a property that has been exploited for commercial production of recombinant proteins. However, the secretory pathway, which is key to the production of extracellular proteins, is rather poorly characterized in filamentous fungi compared to yeast. We report the effects of recombinant protein secretion on gene expression levels in Aspergillus nidulans by directly comparing a bovine chymosin-producing strain with its parental wild-type strain in continuous culture by using expressed sequence tag microarrays. This approach demonstrated more subtle and specific changes in gene expression than those observed when mimicking the effects of protein overproduction by using a secretion blocker. The impact of overexpressing a secreted recombinant protein more closely resembles the unfolded-protein response in vivo.
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Affiliation(s)
- Andrew H Sims
- Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, UK
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Robson GD, Huang J, Wortman J, Archer DB. A preliminary analysis of the process of protein secretion and the diversity of putative secreted hydrolases encoded inAspergillus fumigatus: insights from the genome. Med Mycol 2005; 43 Suppl 1:S41-7. [PMID: 16110791 DOI: 10.1080/13693780400024305] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
The genome sequence of Aspergillus fumigatus has enabled the annotation of genes likely to encode secreted enzymes that may be important in underpinning the natural lifestyle of the fungus and its pathogenicity. We summarize the data from the genome sequence relevant to both the process of protein secretion and the predicted hydrolase enzymes secreted by A. fumigatus.
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Affiliation(s)
- G D Robson
- Faculty of Life Sciences, Stopford Building, University of Manchester, Manchester, M13 9PT, UK
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Nevalainen H, Te'o V, Penttilä M, Pakula T. Heterologous Gene Expression in Filamentous Fungi: A Holistic View. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s1874-5334(05)80011-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
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19
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Al-Sheikh H, Watson AJ, Lacey GA, Punt PJ, MacKenzie DA, Jeenes DJ, Pakula T, Penttilä M, Alcocer MJC, Archer DB. Endoplasmic reticulum stress leads to the selective transcriptional downregulation of the glucoamylase gene in Aspergillus niger. Mol Microbiol 2004; 53:1731-42. [PMID: 15341651 DOI: 10.1111/j.1365-2958.2004.04236.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We describe a new endoplasmic reticulum (ER)-associated stress response in the filamentous fungus Aspergillus niger. The inhibition of protein folding within the ER leads to cellular responses known collectively as the unfolded protein response (UPR) and we show that the selective transcriptional downregulation of the gene encoding glucoamylase, a major secreted protein, but not two non-secreted proteins, is an additional consequence of ER stress. The transcriptional downregulation effect is shown by nuclear run-on studies to be at the level of transcription, rather than mRNA stability, and is found to be mediated through the promoter of glaA in a region more than 1 kb upstream of the translational start. The inhibition of protein folding in the ER can be induced in a variety of ways. We examined the effects of dithiothreitol (DTT), a reducing agent that causes the formation of unfolded proteins. Although a general downregulation of transcription was seen with DTT treatment, we show that selective downregulation was observed with the glaA gene compared with genes encoding the non-secreted proteins gamma-actin and glyceraldehyde 3'-phosphate dehydrogenase. The DTT-treated fungal cells also showed evidence for the induction of the UPR because expression of bipA and pdiA, encoding an ER-resident chaperone and foldase, respectively, are upregulated and splicing of hacA, the gene encoding the transcription factor responsible for induction of the UPR, occurs allowing the production of an active HacA protein. As a preliminary attempt to investigate if the transcriptional downregulation effect was mediated through HacA (i.e. part of the UPR), we examined ER stress induced through antisense technology to lower the level of PDI in the ER of A. niger. Although the transcription of glaA was attenuated in that strain of A. niger, UPR was not evident, suggesting that the transcriptional downregulation mechanism is controlled differently from the UPR.
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Affiliation(s)
- Hashem Al-Sheikh
- School of Biology, University of Nottingham, University Park, Nottingham NG7 2RD, UK
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20
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Zhou H, Zhang Y, Jia C, Yang K. Chaperone characteristics of PDI-related protein A from Aspergillus niger. Biochem Biophys Res Commun 2004; 321:31-7. [PMID: 15358211 DOI: 10.1016/j.bbrc.2004.06.098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2004] [Indexed: 04/30/2023]
Abstract
The functional properties of a novel protein, protein disulfide isomerase-related protein A (PRPA) from Aspergillus niger T21, have been characterized. (1) PRPA possesses disulfide isomerase activity. (2) In Hepes buffer, at substoichiometric concentrations, PRPA facilitates the formation of inactive lysozyme aggregates associated with PRPA (anti-chaperone activity); while at a high molar excess, PRPA inhibits aggregation by maintaining lysozyme in a soluble, yet inactive, state (chaperone-like activity). However, PRPA only exhibits chaperone-like activity during lysozyme refolding in phosphate buffer. (3) Experiments have indicated that disulfide cross-linkage is not required for the interaction between PRPA and lysozyme, and hydrophobic interaction may be responsible for PRPA effect on lysozyme. (4) Co-expression of PRPA and prochymosin in Escherichia coli leads to reduction of inclusion bodies, rendering part of prochymosin molecules soluble yet inactive. The structural and functional characteristics of PRPA suggest that PRPA may play an important role in protein folding, aggregation, and retention in the endoplasmic reticulum.
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Affiliation(s)
- Haiping Zhou
- Institute of Microbiology, Chinese Academe of Sciences, Beijing 100080, China
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21
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Sims AH, Gent ME, Robson GD, Dunn-Coleman NS, Oliver SG. Combining transcriptome data with genomic and cDNA sequence alignments to make confident functional assignments for Aspergillus nidulans genes. ACTA ACUST UNITED AC 2004; 108:853-7. [PMID: 15449589 DOI: 10.1017/s095375620400067x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Whole genome sequencing of several filamentous ascomycetes is complete or in progress; these species, such as Aspergillus nidulans, are relatives of Saccharomyces cerevisiae. However, their genomes are much larger and their gene structure more complex, with genes often containing multiple introns. Automated annotation programs can quickly identify open reading frames for hypothetical genes, many of which will be conserved across large evolutionary distances, but further information is required to confirm functional assignments. We describe a comparative and functional genomics approach using sequence alignments and gene expression data to predict the function of Aspergillus nidulans genes. By highlighting examples of discrepancies between the automated genome annotation and cDNA or EST sequencing, we demonstrate that the greater complexity of gene structure in filamentous fungi demands independent data on gene expression and the gene sequence be used to make confident functional assignments.
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Affiliation(s)
- Andrew H Sims
- School of Biological Sciences, University of Manchester, The Michael Smith Building, Manchester M13 9PT, UK
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22
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Mulder HJ, Saloheimo M, Penttilä M, Madrid SM. The transcription factor HACA mediates the unfolded protein response in Aspergillus niger, and up-regulates its own transcription. Mol Genet Genomics 2004; 271:130-40. [PMID: 14730445 DOI: 10.1007/s00438-003-0965-5] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2003] [Accepted: 11/18/2003] [Indexed: 01/07/2023]
Abstract
The unfolded protein response (UPR) involves a complex signalling pathway in which the transcription factor HACA plays a central role. Here we report the cloning and characterisation of the hacA gene and its product from Aspergillus niger. ER (endoplasmic reticulum) stress results in the splicing of an unconventional 20-nt intron from the A. niger hacA mRNA, and is associated with truncation of the 5'-end of the hacA mRNA by 230 nt. In this study the UPR was triggered by over expressing tissue plasminogen activator (t-PA), and by treatment of mycelia with dithiothreitol (DTT) or tunicamycin. Overexpression of the processed form of hacA not only led to the up-regulation of bipA, cypB and pdiA--mimicking the UPR--but also led to the up-regulation of the hacA gene itself. In vitro binding assays confirmed that the HACA protein binds to the promoters of genes encoding ER-localised chaperones and foldases, and to the promoter of the hacA gene itself. Finally, a GFP-HACA fusion was shown to localise in the nucleus.
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Affiliation(s)
- H J Mulder
- Danisco Innovation Copenhagen, Langebrogade 1, DK 1001 Copenhagen, Denmark.
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23
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Wang H, Entwistle J, Morlon E, Archer DB, Peberdy JF, Ward M, Jeenes DJ. Isolation and characterisation of a calnexin homologue, clxA, from Aspergillus niger. Mol Genet Genomics 2003; 268:684-91. [PMID: 12589443 DOI: 10.1007/s00438-002-0790-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2002] [Accepted: 11/27/2002] [Indexed: 10/25/2022]
Abstract
We describe the isolation of a gene (clxA) encoding calnexin from laboratory and industrial strains of Aspergillus niger. Calnexin is a chaperone, which specifically recognises monoglucosylated glycoproteins in the endoplasmic reticulum, and is thus an essential component of the process that assesses the folded state of nascent secreted glycoproteins. Manipulation of chaperones has previously been adopted in attempts to overcome some of the problems associated with the secretion of heterologous proteins from filamentous fungi. The A. niger clxA gene encodes a 562-residue protein with strong homology to the calnexin of Schizosaccharomyces pombe. The clxAgene product complements a S. pombe cnx1 mutant. Motifs associated with genes controlled via the Unfolded Protein Response (UPR) were identified by sequence homology in the promoter of clxA. Steady-state levels of clxA mRNA were elevated in a strain expressing bovine prochymosin fused to the catalytic domain of glucoamylase. The ORF is punctuated by four introns, and contains two sets of four repeated peptide motifs that are characteristic of the calnexin family, together with a putative membrane-spanning domain. Deletion studies indicate that clxA is not an essential gene in A. niger.
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MESH Headings
- Animals
- Aspergillus niger/genetics
- Aspergillus niger/metabolism
- Base Sequence
- Calnexin/genetics
- Calnexin/metabolism
- Cattle
- Chymosin/biosynthesis
- Chymosin/genetics
- DNA, Fungal/genetics
- Enzyme Precursors/biosynthesis
- Enzyme Precursors/genetics
- Fungal Proteins/genetics
- Fungal Proteins/metabolism
- Gene Deletion
- Gene Expression
- Genes, Fungal
- Genetic Complementation Test
- Glucan 1,4-alpha-Glucosidase/biosynthesis
- Glucan 1,4-alpha-Glucosidase/genetics
- Molecular Sequence Data
- Mutation
- Promoter Regions, Genetic
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/genetics
- Sequence Homology, Amino Acid
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Affiliation(s)
- H Wang
- Genencor International Inc., Palo Alto, CA 94304, USA
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24
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Padilla A, Noiva R, Lee N, Mohan KVK, Nakhasi HL, Debrabant A. An atypical protein disulfide isomerase from the protozoan parasite Leishmania containing a single thioredoxin-like domain. J Biol Chem 2003; 278:1872-8. [PMID: 12427741 DOI: 10.1074/jbc.m210322200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In higher eukaryotes, secretory proteins are under the quality control of the endoplasmic reticulum for their proper folding and release into the secretory pathway. One of the proteins involved in the quality control is protein disulfide isomerase, which catalyzes the formation of protein disulfide bonds. As a first step toward understanding the endoplasmic reticulum quality control of secretory proteins in lower eukaryotes, we have isolated a protein disulfide isomerase gene from the protozoan parasite Leishmania donovani. The parasite enzyme shows high sequence homology with homologs from other organisms. However, unlike the four thioredoxin-like domains found in most protein disulfide isomerases, of which two contain an active site, the leishmanial enzyme possesses only one active site present in a single thioredoxin-like domain. When expressed in Escherichia coli, the recombinant parasite enzyme shows both oxidase and isomerase activities. Replacement of the two cysteins with alanines in its active site results in loss of both enzymatic activities. Further, overexpression of the mutated/inactive form of the parasite enzyme in L. donovani significantly reduced their release of secretory acid phosphatases, suggesting that this single thioredoxin-like domain protein disulfide isomerase could play a critical role in the Leishmania secretory pathway.
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Affiliation(s)
- Alejandro Padilla
- Division of Emerging and Transfusion Transmitted Diseases, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA
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25
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Conesa A, Jeenes D, Archer DB, van den Hondel CAMJJ, Punt PJ. Calnexin overexpression increases manganese peroxidase production in Aspergillus niger. Appl Environ Microbiol 2002; 68:846-51. [PMID: 11823227 PMCID: PMC126695 DOI: 10.1128/aem.68.2.846-851.2002] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Heme-containing peroxidases from white rot basidiomycetes, in contrast to most proteins of fungal origin, are poorly produced in industrial filamentous fungal strains. Factors limiting peroxidase production are believed to operate at the posttranslational level. In particular, insufficient availability of the prosthetic group which is required for peroxidase biosynthesis has been proposed to be an important bottleneck. In this work, we analyzed the role of two components of the secretion pathway, the chaperones calnexin and binding protein (BiP), in the production of a fungal peroxidase. Expression of the Phanerochaete chrysosporium manganese peroxidase (MnP) in Aspergillus niger resulted in an increase in the expression level of the clxA and bipA genes. In a heme-supplemented medium, where MnP was shown to be overproduced to higher levels, induction of clxA and bipA was also higher. Overexpression of these two chaperones in an MnP-producing strain was analyzed for its effect on MnP production. Whereas bipA overexpression seriously reduced MnP production, overexpression of calnexin resulted in a four- to fivefold increase in the extracellular MnP levels. However, when additional heme was provided in the culture medium, calnexin overexpression had no synergistic effect on MnP production. The possible function of these two chaperones in MnP maturation and production is discussed.
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Affiliation(s)
- Ana Conesa
- Department of Applied Microbiology and Gene Technology, TNO Food and Nutrition Research Institute, 3700 AJ Zeist, The Netherlands
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26
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Nigam S, Sarma PV, Ghosh PC, Sarma PU. Characterization of Aspergillus fumigatus protein disulfide isomerase family gene. Gene 2001; 281:143-50. [PMID: 11750136 DOI: 10.1016/s0378-1119(01)00794-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Aspergillus fumigatus is an opportunistic fungus which causes pulmonary complications in humans and animals. The clinical spectrum observed with A. fumigatus is attributed to the multifunctional nature of its antigens. Lack of understanding on the molecular processes and complexity of the fungus have spurred interest in the identification and characterization of its antigens/allergens with biological activities and virulence functions. For identification of some of these antigens/allergens, a cDNA library of A. fumigatus was screened with antibodies of allergic bronchopulmonary aspergillosis (ABPA) patients. One of the reactive clones was sequenced and observed to have an open reading frame of 1095 nucleotides corresponding to a polypeptide of 364 amino acids. The nucleotide and deduced amino acid sequence showed significant homology with the protein disulfide isomerase (PDI) superfamily. The expressed recombinant fusion protein exhibited specific IgG and IgE binding with antibodies present in ABPA patients' sera. The recombinant protein in vitro catalyzed folding of scrambled RNase. The probable epitopic regions of the deduced amino acid sequence were mapped by algorithmic analysis. This is the first report of isolation of a gene encoding a member of the PDI family from A. fumigatus. The PDI superfamily of proteins may play an important role in the protein folding mechanisms of A. fumigatus antigens/allergens for their interaction with the host.
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Affiliation(s)
- S Nigam
- Molecular Biochemistry and Diagnostics Division, Centre for Biochemical Technology, Mall Road, Delhi 110007, India
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27
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McArthur AG, Knodler LA, Silberman JD, Davids BJ, Gillin FD, Sogin ML. The evolutionary origins of eukaryotic protein disulfide isomerase domains: new evidence from the Amitochondriate protist Giardia lamblia. Mol Biol Evol 2001; 18:1455-63. [PMID: 11470836 DOI: 10.1093/oxfordjournals.molbev.a003931] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A phylogenetic analysis of protein disulfide isomerase (PDI) domain evolution was performed with the inclusion of recently reported PDIs from the amitochondriate protist Giardia lamblia, yeast PDIs that contain a single thioredoxin-like domain, and PDIs from a diverse selection of protists. We additionally report and include two new giardial PDIs, each with a single thioredoxin-like domain. Inclusion of protist PDIs in our analyses revealed that the evolutionary history of the endoplasmic reticulum may not be simple. Phylogenetic analyses support common ancestry of all eukaryotic PDIs from a thioredoxin ancestor and independent duplications of thioredoxin-like domains within PDIs throughout eukaryote evolution. This was particularly evident for Acanthamoeba PDI, Dictyostelium PDI, and mammalian erp5 domains. In contrast, gene duplication, instead of domain duplication, produces PDI diversity in G. lamblia. Based on our results and the known diversity of PDIs, we present a new hypothesis that the five single-domain PDIs of G. lamblia may reflect an ancestral mechanism of protein folding in the eukaryotic endoplasmic reticulum. The PDI complement of G. lamblia and yeast suggests that a combination of PDIs may be used as a redox chain analogous to that known for bacterial Dsb proteins.
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Affiliation(s)
- A G McArthur
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, Massachusetts 02543-1015, USA
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28
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Conesa A, Punt PJ, van Luijk N, van den Hondel CA. The secretion pathway in filamentous fungi: a biotechnological view. Fungal Genet Biol 2001; 33:155-71. [PMID: 11495573 DOI: 10.1006/fgbi.2001.1276] [Citation(s) in RCA: 171] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The high capacity of the secretion machinery of filamentous fungi has been widely exploited for the production of homologous and heterologous proteins; however, our knowledge of the fungal secretion pathway is still at an early stage. Most of the knowledge comes from models developed in yeast and higher eukaryotes, which have served as reference for the studies on fungal species. In this review we compile the data accumulated in recent years on the molecular basis of fungal secretion, emphasizing the relevance of these data for the biotechnological use of the fungal cell and indicating how this information has been applied in attempts to create improved production strains. We also present recent emerging approaches that promise to provide answers to fundamental questions on the molecular genetics of the fungal secretory pathway.
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Affiliation(s)
- A Conesa
- Department of Applied Microbiology and Gene Technology, TNO Nutrition and Food Research, Zeist, 3700 AJ, The Netherlands
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29
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Abstract
The knowledge base that will underpin the more efficient use of filamentous fungi as cell factories in food has increased during the past year in the areas of gene regulation, protein secretion, safety and synthesis of ingredients such as long-chain polyunsaturated fatty acids.
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Affiliation(s)
- D B Archer
- School of Life and Environmental Sciences, University of Nottingham, University Park, NG7 2RD, Nottingham, UK.
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