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Ng TB, Cheung RCF, Wong JH, Chan YS, Dan X, Pan W, Wang H, Guan S, Chan K, Ye X, Liu F, Xia L, Chan WY. Fungal proteinaceous compounds with multiple biological activities. Appl Microbiol Biotechnol 2016; 100:6601-6617. [PMID: 27338574 DOI: 10.1007/s00253-016-7671-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 06/02/2016] [Accepted: 06/07/2016] [Indexed: 11/30/2022]
Abstract
Fungi comprise organisms like molds, yeasts and mushrooms. They have been used as food or medicine for a long time. A large number of fungal proteins or peptides with diverse biological activities are considered as antibacterial, antifungal, antiviral and anticancer agents. They encompass proteases, ribosome inactivating proteins, defensins, hemolysins, lectins, laccases, ribonucleases, immunomodulatory proteins, and polysaccharopeptides. The target of the present review is to update the status of the various bioactivities of these fungal proteins and peptides and discuss their therapeutic potential.
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Affiliation(s)
- Tzi Bun Ng
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
| | - Randy Chi Fai Cheung
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
| | - Jack Ho Wong
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
| | - Yau Sang Chan
- State Key Laboratory of Respiratory Disease for Allergy at Shenzhen University, School of Medicine, Shenzhen University, Nanhai Ave 3688, 518060, Shenzhen, Guangdong, People's Republic of China
| | - Xiuli Dan
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Wenliang Pan
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Hexiang Wang
- State Key Laboratory for Agrobiotechnology and Department of Microbiology, China Agricultural University, Beijing, 100193, China
| | - Suzhen Guan
- Department of Social Medicine, College of Public Health, Xinjiang Medical University, Urumqi, 830011, China
| | - Ki Chan
- Biomedical and Tissue Engineering Research Group, Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Hong Kong, China
| | - Xiuyun Ye
- College of Biological Sciences and Technology, Fuzhou University, Fuzhou, Fujian, China.,Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou, Fujian, China
| | - Fang Liu
- Department of Microbiology, Nankai University, Tianjin, China
| | - Lixin Xia
- State Key Laboratory of Respiratory Disease for Allergy at Shenzhen University, School of Medicine, Shenzhen University, Nanhai Ave 3688, 518060, Shenzhen, Guangdong, People's Republic of China
| | - Wai Yee Chan
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
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Khan S, Nadir S, Lihua G, Xu J, Holmes KA, Dewen Q. Identification and characterization of an insect toxin protein, Bb70p, from the entomopathogenic fungus, Beauveria bassiana, using Galleria mellonella as a model system. J Invertebr Pathol 2015; 133:87-94. [PMID: 26592942 DOI: 10.1016/j.jip.2015.11.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 11/19/2015] [Accepted: 11/20/2015] [Indexed: 11/29/2022]
Abstract
An insect-toxic protein, Bb70p, was purified from Beauveria bassiana 70 using ammonium sulfate precipitation, ion exchange chromatography, and gel filtration. Bb70p has a high affinity for anion exchangers and 2D electrophoresis results revealed a single spot with a molecular weight of 35.5 kDa and an iso-electric point of ∼4.5. Bb70p remains active from 4 to 60°C, within a pH range of 4-10, but is more active in slightly acidic pH. A pure protein, Bb70p does not have any carbohydrate side chains. The protein caused high mortality by intra-haemocelic injection into Galleria mellonella with LD50 of 334.4 μg/g body weight and activates the phenol oxidase cascade. With a partial amino acid sequence comparison using the NCBI database, we showed no homology to known toxin proteins of entomopathogenic fungi. Thus, Bb70p appears to be an insect toxin protein, demonstrating novelty. Identification of this insect-toxic protein presents potential to enhance the virulence of B. bassiana through genetic manipulation.
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Affiliation(s)
- Sehroon Khan
- The World Agroforestry Centre, East and Central Asia, 132 Lanhei Rd, Heilongtan, Kunming 650201, Yunnan, China; Centre for Mountain Ecosystem Studies, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, Yunnan, China; Key Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 12 Zhong-guancun South Street, Beijing 100081, People's Republic of China
| | - Sadia Nadir
- Rice Research Institute, Yunnan Agriculture University, Heilongtan, Kunming 650201, Yunnan, China; Department of Chemistry, Faculty of Sciences, University of Science and Technology Bannu, Khyber Pakhtunkhwa, 28100 Bannu, Pakistan
| | - Guo Lihua
- Key Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 12 Zhong-guancun South Street, Beijing 100081, People's Republic of China
| | - Jianchu Xu
- The World Agroforestry Centre, East and Central Asia, 132 Lanhei Rd, Heilongtan, Kunming 650201, Yunnan, China; Centre for Mountain Ecosystem Studies, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, Yunnan, China
| | | | - Qiu Dewen
- Key Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 12 Zhong-guancun South Street, Beijing 100081, People's Republic of China.
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3
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Yadav SK, Batra JK. Ribotoxin restrictocin manifests anti-HIV-1 activity through its specific ribonuclease activity. Int J Biol Macromol 2015; 76:58-62. [PMID: 25709025 DOI: 10.1016/j.ijbiomac.2015.01.062] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 01/23/2015] [Accepted: 01/27/2015] [Indexed: 01/18/2023]
Abstract
Restrictocin, a highly specific ribonuclease produced by Aspergillus restrictus, cleaves a single phosphodiester bond in a universally conserved stem and loop structure termed sarcin/ricin loop within the large ribosomal RNA of all organisms. In the current study, we demonstrate restrictocin to manifest anti-HIV-1 activity in two model cell systems. Using two mutants of restrictocin, we further show that the anti-HIV-1 activity of restrictocin is due to its specific ribonucleolytic activity. The study suggests that restrictocin is able to recognize region(s) within HIV-1 genome as its target. Restrictocin appears to have potential as a therapeutic antiviral agent against HIV-1.
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Affiliation(s)
- Santosh K Yadav
- Immunochemistry Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Janendra K Batra
- Immunochemistry Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India; Centre for Molecular Medicine, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
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4
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Kobayashi H, Motoyoshi N, Itagaki T, Inokuchi N. Mutagenesis of the novel Hericium erinaceus ribonuclease, RNase He1, reveals critical responsible residues for enzyme stability and activity. Biol Pharm Bull 2014; 37:1843-7. [PMID: 25366489 DOI: 10.1248/bpb.b14-00553] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Here, we determined the sequence of a cDNA encoding a guanylic acid-specific ribonuclease (RNase He1) from Hericium erinaceus that exhibits high sequence identity (59%) with RNase Po1, an enzyme with anti-cancer activity and which is found in Pleurotus ostreatus. RNase He1 and RNase Po1 have similar structures and heat stabilities; hence, RNase He1 may also have potential as an anti-cancer agent. Therefore, we initiated structure-function studies to further characterize the enzyme. Based on the RNase Po1 structure, RNase He1 is predicted to form 3 disulfide bonds involving Cys7-Cys98, Cys5-Cys83, and Cys47-Cys81 linkages. The Cys5Ala mutant exhibited no RNase activity, whereas the Cys81Ala mutant retained RNase activity, but had reduced heat stability. Therefore, the Cys5-Cys83 bond in RNase He1 is essential for the structure of the RNase active site region. Similarly, the Cys47-Cys81 bond helps maintain the conformational stability of the active site region, and may contribute to the greater heat stability of RNase He1.
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Kobayashi H, Motoyoshi N, Itagaki T, Suzuki M, Inokuchi N. Effect of the replacement of aspartic acid/glutamic acid residues with asparagine/glutamine residues in RNase He1 from Hericium erinaceus on inhibition of human leukemia cell line proliferation. Biosci Biotechnol Biochem 2014; 79:211-7. [PMID: 25338779 DOI: 10.1080/09168451.2014.972327] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
RNase He1 from Hericium erinaceus, a member of the RNase T1 family, has high identity with RNase Po1 from Pleurotus ostreatus with complete conservation of the catalytic sequence. However, the optimal pH for RNase He1 activity is lower than that of RNase Po1, and the enzyme shows little inhibition of human tumor cell proliferation. Hence, to investigate the potential antitumor activity of recombinant RNase He1 and to possibly enhance its optimum pH, we generated RNase He1 mutants by replacing 12 Asn/Gln residues with Asp/Glu residues; the amino acid sequence of RNase Po1 was taken as reference. These mutants were then expressed in Escherichia coli. Using site-directed mutagenesis, we successfully modified the optimal pH for enzyme activity and generated a recombinant RNase He1 that inhibited the proliferation of cells in the human leukemia cell line. These properties are extremely important in the production of anticancer biologics that are based on RNase activity.
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Affiliation(s)
- Hiroko Kobayashi
- a Department of Microbiology, School of Pharmacy , Nihon University , Chiba , Japan
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The inhibition of human tumor cell proliferation by RNase Pol, a member of the RNase T1 family, from Pleurotus ostreatus. Biosci Biotechnol Biochem 2013; 77:1486-91. [PMID: 23832341 DOI: 10.1271/bbb.130133] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
RNase Po1 is a guanylic acid-specific ribonuclease (a RNase T1 family RNase) from Pleurotus ostreatus. We determined the cDNA sequence encoding RNase Po1 and expressed RNase Po1 in Escherichia coli. A comparison of the enzymatic properties of RNase Po1 and RNase T1 indicated that the optimum temperature for RNase Po1 activity was 20 °C higher than that for RNase T1. An MTT assay indicated that RNase Po1 inhibits the proliferation of human neuroblastoma cells (IMR-32 and SK-N-SH) and human leukemia cells (Jurkat and HL-60). Furthermore, Hoechst 33342 staining showed morphological changes in HL-60 cells due to RNase Po1, and flow cytometry indicated the appearance of a sub-G1 cell population. The extent of these changes was dependent on the concentration of RNase Pol. We suggest that RNase Po1 induces apoptosis in tumor cells.
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Hirsutellin A: A Paradigmatic Example of the Insecticidal Function of Fungal Ribotoxins. INSECTS 2013; 4:339-56. [PMID: 26462423 PMCID: PMC4553468 DOI: 10.3390/insects4030339] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 06/21/2013] [Accepted: 06/24/2013] [Indexed: 11/17/2022]
Abstract
The fungal pathogen Hirsutella thompsonii produces an insecticidal protein named hirsutellin A (HtA), which has been described to be toxic to several species of mites, insect larvae, and cells. On the other hand, on the basis of an extensive biochemical and structural characterization, HtA has been considered to be a member of the ribotoxins family. Ribotoxins are fungal extracellular ribonucleases, which inactivate ribosomes by specifically cleaving a single phosphodiester bond located at the large rRNA. Although ribotoxins were brought to light in the 1960s as antitumor agents, their biological function has remained elusive. Thus, the consideration of hirsutellin A, an insecticidal protein, as a singular ribotoxin recalled the idea of the biological activity of these toxins as insecticidal agents. Further studies have demonstrated that the most representative member of the ribotoxin family, α-sarcin, also shows strong toxic action against insect cells. The determination of high resolution structures, the characterization of a large number of mutants, and the toxicity assays against different cell lines have been the tools used for the study of the mechanism of action of ribotoxins at the molecular level. The aim of this review is to serve as a compilation of the facts that allow identification of HtA as a paradigmatic example of the insecticidal function of fungal ribotoxins.
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Plantinga MJ, Korennykh AV, Piccirilli JA, Correll CC. The ribotoxin restrictocin recognizes its RNA substrate by selective engagement of active site residues. Biochemistry 2011; 50:3004-13. [PMID: 21417210 PMCID: PMC3071035 DOI: 10.1021/bi1018336] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
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Restrictocin and related fungal endoribonucleases from the α-sarcin family site-specifically cleave the sarcin/ricin loop (SRL) on the ribosome to inhibit translation and ultimately trigger cell death. Previous studies showed that the SRL folds into a bulged-G motif and tetraloop, with restrictocin achieving a specificity of ∼1000-fold by recognizing both motifs only after the initial binding step. Here, we identify contacts within the protein−RNA interface and determine the extent to which each one contributes to enzyme specificity by examining the effect of protein mutations on the cleavage of the SRL substrate compared to a variety of other RNA substrates. As with other biomolecular interfaces, only a subset of contacts contributes to specificity. One contact of this subset is critical, with the H49A mutation resulting in quantitative loss of specificity. Maximum catalytic activity occurs when both motifs of the SRL are present, with the major contribution involving the bulged-G motif recognized by three lysine residues located adjacent to the active site: K110, K111, and K113. Our findings support a kinetic proofreading mechanism in which the active site residues H49 and, to a lesser extent, Y47 make greater catalytic contributions to SRL cleavage than to suboptimal substrates. This systematic and quantitative analysis begins to elucidate the principles governing RNA recognition by a site-specific endonuclease and may thus serve as a mechanistic model for investigating other RNA modifying enzymes.
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Affiliation(s)
- Matthew J Plantinga
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637, USA
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9
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Tourlakis ME, Karran RA, Desouza L, Siu KWM, Hudak KA. Homodimerization of pokeweed antiviral protein as a mechanism to limit depurination of pokeweed ribosomes. MOLECULAR PLANT PATHOLOGY 2010; 11:757-767. [PMID: 21029321 PMCID: PMC6640456 DOI: 10.1111/j.1364-3703.2010.00640.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Ribosome inactivating proteins are glycosidases synthesized by many plants and have been hypothesized to serve in defence against pathogens. These enzymes catalytically remove a conserved purine from the sarcin/ricin loop of the large ribosomal RNA, which has been shown in vitro to limit protein synthesis. The resulting toxicity suggests that plants may possess a mechanism to protect their ribosomes from depurination during the synthesis of these enzymes. For example, pokeweed antiviral protein (PAP) is cotranslationally inserted into the lumen of the endoplasmic reticulum and travels via the endomembrane system to be stored in the cell wall. However, some PAP may retrotranslocate across the endoplasmic reticulum membrane to be released back into the cytosol, thereby exposing ribosomes to depurination. In this work, we isolated and characterized a complexed form of the enzyme that exhibits substantially reduced activity. We showed that this complex is a homodimer of PAP and that dimerization involves a peptide that contains a conserved aromatic amino acid, tyrosine 123, located in the active site of the enzyme. Bimolecular fluorescence complementation demonstrated that the homodimer may form in vivo and that dimerization is prevented by the substitution of tyrosine 123 for alanine. The homodimer is a minor form of PAP, observed only in the cytosol of cells and not in the apoplast. Taken together, these data support a novel mechanism for the limitation of depurination of autologous ribosomes by molecules of the protein that escape transport to the cell wall by the endomembrane system.
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Endo Y, Morishita R, Imashevich KM, Yoshinari S. Mechanisms of Action of Ribotoxins. ACTA ACUST UNITED AC 2009. [DOI: 10.3109/15569549809040402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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11
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Álvarez-García E, Martínez-del-Pozo Á, Gavilanes JG. Role of the basic character of α-sarcin’s NH2-terminal β-hairpin in ribosome recognition and phospholipid interaction. Arch Biochem Biophys 2009; 481:37-44. [DOI: 10.1016/j.abb.2008.10.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2008] [Revised: 10/06/2008] [Accepted: 10/07/2008] [Indexed: 11/17/2022]
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Lacadena J, Alvarez-García E, Carreras-Sangrà N, Herrero-Galán E, Alegre-Cebollada J, García-Ortega L, Oñaderra M, Gavilanes JG, Martínez del Pozo A. Fungal ribotoxins: molecular dissection of a family of natural killers. FEMS Microbiol Rev 2007; 31:212-37. [PMID: 17253975 DOI: 10.1111/j.1574-6976.2006.00063.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
RNase T1 is the best known representative of a large family of ribonucleolytic proteins secreted by fungi, mostly Aspergillus and Penicillium species. Ribotoxins stand out among them by their cytotoxic character. They exert their toxic action by first entering the cells and then cleaving a single phosphodiester bond located within a universally conserved sequence of the large rRNA gene, known as the sarcin-ricin loop. This cleavage leads to inhibition of protein biosynthesis, followed by cellular death by apoptosis. Although no protein receptor has been found for ribotoxins, they preferentially kill cells showing altered membrane permeability, such as those that are infected with virus or transformed. Many steps of the cytotoxic process have been elucidated at the molecular level by means of a variety of methodological approaches and the construction and purification of different mutant versions of these ribotoxins. Ribotoxins have been used for the construction of immunotoxins, because of their cytotoxicity. Besides this activity, Aspf1, a ribotoxin produced by Aspergillus fumigatus, has been shown to be one of the major allergens involved in allergic aspergillosis-related pathologies. Protein engineering and peptide synthesis have been used in order to understand the basis of these pathogenic mechanisms as well as to produce hypoallergenic proteins with potential diagnostic and immunotherapeutic applications.
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Affiliation(s)
- Javier Lacadena
- Departamento de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
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Crameri R, Limacher A, Weichel M, Glaser AG, Zeller S, Rhyner C. Structural aspects and clinical relevance of Aspergillus fumigatus antigens/allergens. Med Mycol 2006; 44:S261-S267. [PMID: 30408912 DOI: 10.1080/13693780600789160] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Robotics-based high throughput screening of Aspergillus fumigatus cDNA libraries displayed on phage surfaces revealed at last 81 different structures able to bind IgE from serum of patients sensitized to this fungus. Among these, species-specific as well as phylogenetically highly conserved structures and such with unknown function have been detected. A subset of cDNAs have been used to produce and characterize the corresponding recombinant allergens which have proven to be useful diagnostic reagents allowing specific detection of A. fumigatus sensitization and differential diagnosis of allergic bronchopulmonary aspergillosis. Phylogenetically highly conserved structures like manganese-dependent superoxide dismutase, P2 acidic ribosomal protein, cyclophilins and thioredoxins induce, beyond sensitization, IgE antibodies able to cross-react with the corresponding homologous self antigens. These reactions, likely to contribute to the exacerbation and perpetuation of allergic bronchopulmonary aspergillosis, can be traced back to shared conformational B-cell epitopes build up from conserved amino acid residues scattered over the surface of the molecules as shown by detailed analyses of the crystal structures.
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Affiliation(s)
- R Crameri
- Swiss Institute of Allergy and Asthma Research (SIAF), Davos, Switzerland
| | - A Limacher
- Swiss Institute of Allergy and Asthma Research (SIAF), Davos, Switzerland
| | - M Weichel
- Swiss Institute of Allergy and Asthma Research (SIAF), Davos, Switzerland
| | - A G Glaser
- Swiss Institute of Allergy and Asthma Research (SIAF), Davos, Switzerland
| | - S Zeller
- Swiss Institute of Allergy and Asthma Research (SIAF), Davos, Switzerland
| | - C Rhyner
- Swiss Institute of Allergy and Asthma Research (SIAF), Davos, Switzerland
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Alvarez-García E, García-Ortega L, Verdún Y, Bruix M, Martínez del Pozo A, Gavilanes JG. Tyr-48, a conserved residue in ribotoxins, is involved in the RNA-degrading activity of α-sarcin. Biol Chem 2006; 387:535-41. [PMID: 16740124 DOI: 10.1515/bc.2006.069] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Residue Tyr-48 in alpha-sarcin is conserved not only within the ribotoxin family, but also within the larger group of extracellular fungal ribonucleases, best represented by RNase T1. A mutant protein in which this Tyr residue was substituted by Phe has been produced and isolated to homogeneity. It was spectroscopically analyzed by means of circular dichroism, fluorescence emission and NMR. Taken together, these results and those from enzyme characterization have revealed the essential role of the -OH group from the Tyr-48 phenolic ring in the cleavage of polymeric RNA substrates, including the ribosome-embedded 28S rRNA, the natural substrate of ribotoxins. Thus, the mutant protein does not degrade its natural ribosomal RNA substrate. However, it has been shown that this Y48F mutant still retains its ability to cleave a phosphodiester bond in a minimal substrate such as the dinucleoside phosphate ApA. The role of different alpha-sarcin residues within the enzyme reaction catalyzed by this protein is discussed.
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Affiliation(s)
- Elisa Alvarez-García
- Departamento de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense, E-28040 Madrid, Spain
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Garciá-Ortega L, Lacadena J, Villalba M, Rodríguez R, Crespo JF, Rodríguez J, Pascual C, Olmo N, Oñaderra M, del Pozo AM, Gavilanes JG. Production and characterization of a noncytotoxic deletion variant of the Aspergillus fumigatus allergen Aspf1 displaying reduced IgE binding. FEBS J 2005; 272:2536-44. [PMID: 15885102 DOI: 10.1111/j.1742-4658.2005.04674.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Aspergillus fumigatus is responsible for many allergic respiratory diseases, the most notable of which - due to its severity - is allergic bronchopulmonary aspergillosis. Aspf1 is a major allergen of this fungus: this 149-amino acid protein belongs to the ribotoxin family, whose best characterized member is alpha-sarcin (EC 3.1.27.10). The proteins of this group are cytotoxic ribonucleases that degrade a unique bond in ribosomal RNA impairing protein biosynthesis. Aspf1 and its deletion mutant Aspf1Delta(7-22) have been produced as recombinant proteins; the deleted region corresponds to an exposed beta-hairpin. The conformation of these two proteins has been studied by CD and fluorescence spectroscopy. Their enzymatic activity and cytotoxicity against human rhabdomyosarcoma cells was also measured and their allergenic properties have been studied by using 58 individual sera of patients sensitized to Aspergillus. Aspf1Delta(7-22) lacks cytotoxicity and shows a remarkably reduced IgE reactivity. From these studies it can be concluded that the deleted beta-hairpin is involved in ribosome recognition and is a significant allergenic region.
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Affiliation(s)
- Lucía Garciá-Ortega
- Departamento de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense, Madrid, Spain
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Quesada-Moraga E, Vey A. Bassiacridin, a protein toxic for locusts secreted by the entomopathogenic fungus Beauveria bassiana. ACTA ACUST UNITED AC 2004; 108:441-52. [PMID: 15209284 DOI: 10.1017/s0953756204009724] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A toxic protein, bassiacridin, was purified from a strain of the entomopathogenic fungus Beauveria bassiana isolated from a locust, using chromatographic methods. The final toxic fraction contained between 0.1 and 0.3% of the proteins of the crude extract. Bassiacridin showed no affinity for ion exchangers, was characterised as a monomer with a mol. wt of 60 kDa and an isoelectric point of 9.5, and exhibited beta-glucosidase, beta-galactosidase and N-acetylglucosaminidase activities. Injection of fourth instar nymphs of Locusta migratoria with the pure protein at relatively low dosage (3.3 microg toxin g body wt(-1)) caused a rate of mortality near to 50%. The effects of the crude and pure fractions were characterized at tissular and cellular levels. The formation of melanised spots on tracheae and air sacs and of melanised nodules in contact with the fat body was observed in injected locusts. Alterations of the fine structure of epithelial cells of tracheae, air bags, and integument were also revealed. The insecticidal protein showed a specific activity against locusts. Bassiacridin is different from the other macromolecular toxins of entomopathogenic fungi already described. Microsequencing of peptides generated by trypsic digestion of bassiacridin confirmed that it is a novel molecule and showed that it exhibits a probably limited similarity with a chitin binding protein from yeast.
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Affiliation(s)
- Enrique Quesada-Moraga
- Laboratoire de Recherches de Pathologie Comparée, INRA, 30380 Saint Christol lez Alès, France
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Goyal A, Seth D, Batra JK. Role of cis prolines 112 and 126 in the functional activity of ribonucleolytic toxin restrictocin. Biochem Biophys Res Commun 2002; 295:812-7. [PMID: 12127966 DOI: 10.1016/s0006-291x(02)00780-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Restrictocin is a 149 amino acid ribonucleolytic toxin produced by the fungus Aspergillus, which specifically cleaves a single phosphodiester bond within 28S rRNA resulting in a potent inhibition of protein synthesis in eukaryotic cells. Restrictocin has 12 prolines out of which three at positions 48, 112, and 126 are cis. Prolines at position 112, 118, and 126 were individually mutated to alanine to investigate their role in the catalytic and membrane interaction activity of restrictocin. All mutants were expressed in Escherichia coli, and recombinant proteins purified to homogeneity. Mutation of P112 resulted in a remarkable 50- and 100-fold reduction, respectively, in the ribonucleolytic and cytotoxic activities of restrictocin, whereas the interaction of P112A with phospholipid membranes increased. Mutants P118A and P126A exhibited 3-5-fold decreased ribonucleolytic and cytotoxic activities, however, their membrane interaction activity was marginally reduced compared to restrictocin. The study demonstrates that P112 is absolutely essential to maintain the functionally active conformation of restrictocin. Also, prolines 112, 118, and 126 do not appear to be directly involved in the membrane interaction activity of restrictocin.
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Affiliation(s)
- Anita Goyal
- Immunochemistry Laboratory, National Institute of Immunology, Aruna Asaf Ali Road, New Delhi, India
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18
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Garcia-Ortega L, Masip M, Mancheño JM, Oñaderra M, Lizarbe MA, García-Mayoral MF, Bruix M, Martínez del Pozo A, Gavilanes JG. Deletion of the NH2-terminal beta-hairpin of the ribotoxin alpha-sarcin produces a nontoxic but active ribonuclease. J Biol Chem 2002; 277:18632-9. [PMID: 11897788 DOI: 10.1074/jbc.m200922200] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ribotoxins are a family of highly specific fungal ribonucleases that inactivate the ribosomes by hydrolysis of a single phosphodiester bond of the 28 S rRNA. alpha-Sarcin, the best characterized member of this family, is a potent cytotoxin that promotes apoptosis of human tumor cells after internalization via endocytosis. This latter ability is related to its interaction with phospholipid bilayers. These proteins share a common structural core with nontoxic ribonucleases of the RNase T1 family. However, significant structural differences between these two groups of proteins are related to the presence of a long amino-terminal beta-hairpin in ribotoxins and to the different length of their unstructured loops. The amino-terminal deletion mutant Delta(7-22) of alpha-sarcin has been produced in Escherichia coli and purified to homogeneity. It retains the same conformation as the wild-type protein as ascertained by complete spectroscopic characterization based on circular dichroism, fluorescence, and NMR techniques. This mutant exhibits ribonuclease activity against naked rRNA and synthetic substrates but lacks the specific ability of the wild-type protein to degrade rRNA in intact ribosomes. The results indicate that alpha-sarcin interacts with the ribosome at two regions, i.e. the well known sarcin-ricin loop of the rRNA and a different region recognized by the beta-hairpin of the protein. In addition, this latter protein portion is involved in interaction with cell membranes. The mutant displays decreased interaction with lipid vesicles and shows behavior compatible with the absence of one vesicle-interacting region. In agreement with this conclusion, the deletion mutant exhibits a very low cytotoxicity on human rhabdomyosarcoma cells.
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Affiliation(s)
- Lucia Garcia-Ortega
- Departamento de Bioquimica y Biologia Molecular I, Universidad Complutense, Madrid 28040, Spain
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19
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Martínez-Ruiz A, García-Ortega L, Kao R, Lacadena J, Oñaderra M, Mancheño JM, Davies J, Martínez del Pozo A, Gavilanes JG. RNase U2 and alpha-sarcin: a study of relationships. Methods Enzymol 2002; 341:335-51. [PMID: 11582789 DOI: 10.1016/s0076-6879(01)41162-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- A Martínez-Ruiz
- Centro de Investigaciones Biologicas-CSIC, E-28006 Madrid, Spain
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20
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Glück A, Wool IG. Analysis by systematic deletion of amino acids of the action of the ribotoxin restrictocin. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1594:115-26. [PMID: 11825614 DOI: 10.1016/s0167-4838(01)00290-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A series of contiguous deletions were made in a cDNA encoding the ribonuclease restrictocin with the purpose of identifying the amino acids that are essential for the cleavage of the phosphodiester bond on the 3' side of G4325 in the alpha-sarcin/ricin domain of mammalian (rat) 28S rRNA. In all 93 of 149 amino acids, 62% of the residues in restrictocin, were not essential for the action of the toxin. Of the five residues that have been proposed to constitute the active site, three could be deleted without loss of activity if they were part of a deletion of three or five amino acids but not if they were removed singly. It is likely that the loss of these three residues is compensated for by a neighboring residue that occupies the structural space created by the larger amino acid deletions. This was demonstrated to be the case for the active site residue Glu95 which in the deletion mutant Delta91-95 is replaced by Asp90. Systematic deletion of amino acids is a rapid, cost effective method for identifying the residues in a protein likely to contribute directly to function and, hence, deserving of closer scrutiny. Moreover, a semiquantitative estimate of the contribution of the residue to function can be made. For this reason the method may be useful for functional proteomics.
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Affiliation(s)
- Anton Glück
- Department of Biochemistry and Molecular Biology, University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA
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21
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Masip M, Lacadena J, Mancheño JM, Oñaderra M, Martínez-Ruiz A, Martínez del Pozo A, Gavilanes JG. Arginine 121 is a crucial residue for the specific cytotoxic activity of the ribotoxin alpha-sarcin. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:6190-6. [PMID: 11733014 DOI: 10.1046/j.0014-2956.2001.02566.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Alpha-sarcin, a cyclizing ribonuclease secreted by the mould Aspergillus giganteus, is one of the best characterized members of a family of fungal ribotoxins. This protein induces apoptosis in tumour cells due to its highly specific activity on ribosomes. Fungal ribotoxins display a three-dimensional protein fold similar to those of a larger group of microbial noncytotoxic RNases, represented by RNases T1 and U2. This similarity involves the three catalytic residues and also the Arg121 residue, whose counterpart in RNase T1, Arg77, is located in the vicinity of the substrate phosphate moiety although its potential functional role is not known. In this work, Arg121 of alpha-sarcin has been replaced by Gln or Lys. These two mutations do not modify the conformation of the protein but abolish the ribosome-inactivating activity of alpha-sarcin. In addition, the loss of the positive charge at that position produces dramatic changes on the interaction of alpha-sarcin with phospholipid membranes. It is concluded that Arg121 is a crucial residue for the characteristic cytotoxicity of alpha-sarcin and presumably of the other fungal ribotoxins.
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Affiliation(s)
- M Masip
- Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense, Madrid, Spain
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22
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Wang HX, Ng TB. Isolation of a novel ubiquitin-like protein from Pleurotus ostreatus mushroom with anti-human immunodeficiency virus, translation-inhibitory, and ribonuclease activities. Biochem Biophys Res Commun 2000; 276:587-93. [PMID: 11027517 DOI: 10.1006/bbrc.2000.3540] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A glycoprotein, with a ubiquitin-like N-terminal sequence, has been prepared from an extract of fruiting bodies of the mushroom Pleurotus ostreatus, using a procedure which included ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on SP-Sepharose and Mono Q and gel filtration on Superdex 75. It exhibited a molecular weight of 12.5 kDa and was unadsorbed on DEAE-cellulose and Mono Q, but adsorbed on Affi-blue gel and SP-Sepharose. It inhibited translation in a rabbit reticulocyte lysate system (IC(50) = 160 nM) and exhibited low ribonucleolytic activity (14 micro/mg) toward yeast tRNA. It also expressed an inhibitory activity toward human immunodeficiency virus-1 reverse transcriptase, which could be enhanced by succinylation.
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Affiliation(s)
- H X Wang
- Department of Microbiology, China Agricultural University, Beijing, China
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23
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Hwu L, Huang K, Chen D, Lin A. The action mode of the ribosome-inactivating protein alpha-sarcin. J Biomed Sci 2000; 7:420-8. [PMID: 10971140 DOI: 10.1007/bf02255817] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Based on the tertiary structure of the ribosome-inactivating protein alpha-sarcin, domains that are responsible for hydrolyzing ribosomes and naked RNA have been dissected. In this study, we found that the head-to-tail interaction between the first amino beta-strand and the last carboxyl beta-strand is not involved in catalyzing the hydrolysis of ribosomes or ribonucleic acids. Instead, a four-strand pleated beta-sheet is indispensable for catalyzing both substrates, suggesting that alpha-sarcin and ribonuclease T1 (RNase T1) share a similar catalytic center. The integrity of an amino beta-hairpin and that of the loop L3 in alpha-sarcin are crucial for recognizing and hydrolyzing ribosomes in vitro and in vivo. However, a mutant protein without the beta-hairpin structure, or with a disrupted loop L3, is still capable of digesting ribonucleic acids. The functional involvement of the beta-hairpin and the loop L3 in the sarcin stem/loop RNA of ribosomes is demonstrated by a docking model, suggesting that the two structures are in essence naturally designed to distinguish ribosome-inactivating proteins from RNase T1 to inactivate ribosomes.
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Affiliation(s)
- L Hwu
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, ROC
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24
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García-Ortega L, Lacadena J, Lacadena V, Masip M, De Antonio C, Martínez-Ruiz A, Martínez Del Pozo A. The solubility of the ribotoxin alpha-sarcin, produced as a recombinant protein in Escherichia coli, is increased in the presence of thioredoxin. Lett Appl Microbiol 2000; 30:298-302. [PMID: 10792650 DOI: 10.1046/j.1472-765x.2000.00714.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The yield of purified recombinant alpha-sarcin increases approximately three- to fourfold when this toxin is co-expressed in Escherichia coli with thioredoxin. This increased production is attributed to the existence, in the presence of thioredoxin, of a reducing environment which allows rearrangement of incorrect disulphide bonds to produce the soluble native conformation. The protein thus produced retains the structural, spectroscopic and enzymatic features of the natural fungal alpha-sarcin.
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Affiliation(s)
- L García-Ortega
- Departamento de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense, Madrid, Spain
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25
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Nayak SK, Batra JK. Localization of the catalytic activity in restrictocin molecule by deletion mutagenesis. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:1777-83. [PMID: 10712610 DOI: 10.1046/j.1432-1327.2000.01176.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Restrictocin, produced by the fungus Aspergillus restrictus, is a highly specific ribonucleolytic toxin which cleaves a single phosphodiester bond between G4325 and A4326 in the 28S rRNA. It is a nonglycosylated, single-chain, basic protein of 149 amino acids. The putative catalytic site of restrictocin includes Tyr47, His49, Glu95, Arg120 and His136. To map the catalytic activity in the restrictocin molecule, and to study the role of N- and C-terminus in its activity, we have systematically deleted amino-acid residues from both the termini. Three N-terminal deletions removing 8, 15 and 30 amino acids, and three C-terminal deletions lacking 4, 6, and 11 amino acids were constructed. The deletion mutants were expressed in Escherichia coli, purified to homogeneity and functionally characterized. Removal of eight N-terminal or four C-terminal amino acids rendered restrictocin partially inactive, whereas any further deletions from either end resulted in the complete inactivation of the toxin. The study demonstrates that intact N- and C-termini are required for the optimum functional activity of restrictocin.
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Affiliation(s)
- S K Nayak
- Immunochemistry Laboratory, National Institute of Immunology, New Delhi, India
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26
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Kao R, Davies J. Single amino acid substitutions affecting the specificity of the fungal ribotoxin mitogillin. FEBS Lett 2000; 466:87-90. [PMID: 10648818 DOI: 10.1016/s0014-5793(99)01753-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Mitogillin and related fungal ribotoxins are small basic ribonucleolytic proteins that inhibit protein synthesis by specifically hydrolyzing a single phosphodiester bond in the universally conserved alpha-sarcin/ricin loop (SRL) of large subunit ribosomal RNAs. It was previously shown that mitogillin is a natural derivative of a T1/U2-like ribonuclease with inserted domains that are involved in target selection and specificity. Site-directed mutagenesis was used to substitute single amino acids in the previously identified functional domains Ala1-Tyr24 (B1-L1-B2 domain) and Lys106-Lys113 (L4 region). Examination of the activities of the mutants in the digestion of polyinosinic acid (a ribonuclease substrate) and specific cleavage of the SRL shows that Asn7Ala and Lys111Gln substitutions lead to altered ribonuclease activity and diminished substrate specificity consistent with the proposed functions of these domains.
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Affiliation(s)
- R Kao
- Department of Microbiology and Immunology, The University of British Columbia, 6174 University Blvd., Vancouver, B.C., Canada.
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27
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Lacadena J, Martínez del Pozo A, Martínez-Ruiz A, Pérez-Cañadillas JM, Bruix M, Mancheño JM, Oñaderra M, Gavilanes JG. Role of histidine-50, glutamic acid-96, and histidine-137 in the ribonucleolytic mechanism of the ribotoxin alpha-sarcin. Proteins 1999; 37:474-84. [PMID: 10591106 DOI: 10.1002/(sici)1097-0134(19991115)37:3<474::aid-prot14>3.0.co;2-n] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
alpha-Sarcin is a ribotoxin secreted by the mold Aspergillus giganteus that degrades the ribosomal RNA by acting as a cyclizing ribonuclease. Three residues potentially involved in the mechanism of catalysis--histidine-50, glutamic acid-96, and histidine-137--were changed to glutamine. Three different single mutation variants (H50Q, E96Q, H137Q) as well as a double variant (H50/137Q) and a triple variant (H50/137Q/E96Q) were prepared and isolated to homogeneity. These variants were spectroscopically (circular dichroism, fluorescence emission, and proton nuclear magnetic resonance) characterized. According to these results, the three-dimensional structure of these variants of alpha-sarcin was preserved; only very minor local changes were detected. All the variants were inactive when assayed against either intact ribosomes or poly(A). The effect of pH on the ribonucleolytic activity of alpha-sarcin was evaluated against the ApA dinucleotide. This assay revealed that only the H50Q variant still retained its ability to cleave a phosphodiester bond, but it did so to a lesser extent than did wild-type alpha-sarcin. The results obtained are interpreted in terms of His137 and Glu96 as essential residues for the catalytic activity of alpha-sarcin (His137 as the general acid and Glu96 as the general base) and His50 stabilizing the transition state of the reaction catalyzed by alpha-sarcin.
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Affiliation(s)
- J Lacadena
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain
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28
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Martínez-Ruiz A, Kao R, Davies J, Martínez del Pozo A. Ribotoxins are a more widespread group of proteins within the filamentous fungi than previously believed. Toxicon 1999; 37:1549-63. [PMID: 10482390 DOI: 10.1016/s0041-0101(99)00103-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Alpha-sarcin, restrictocin and mitogillin are the best known members of the family of fungal ribotoxins. In recent years, new members of this family have been discovered and characterised. In this work, we study the occurrence of ribotoxins among different species of fungi. The presence of ribotoxins has been identified in some new species by means of genetic studies, as well as expression and activity assays. The ribotoxin genes have been partially sequenced, and demonstrate a high degree of similarity. These studies demonstrate that these toxins are more widespread than previously considered. This is surprising, considering the ribotoxins are such specific and potent toxins, of unknown biological function. These studies confirm the hypothesis that these proteins are naturally engineered toxins derived from ribonucleases of broad substrate specificity.
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Affiliation(s)
- A Martínez-Ruiz
- Departamento de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense de Madrid, Spain
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29
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Bir N, Paliwal A, Muralidhar K, Sarma PU. Biochemical characterization of an immunodominant allergen/antigen ofAspergillus fumigatus. Indian J Clin Biochem 1999; 14:149-58. [PMID: 23105213 DOI: 10.1007/bf02867913] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
An 18kDa protein was identified as a major immunodominant allergen/antigen secreted by a wild type isolate and various clinical isolates ofA. fumigatus. The protein was purified to homogeneity and the N-terminal amino acid was found to be alanine. The N-terminal 20 amino acid sequence of 18kDa was found to be similar to restrictocin, a cytotoxin secreted byAspergillus restrictus. Mass spectroscopic analysis of the purified allergen revealed a molecular size of 17.01 kDa. Immunoreactivity of the purified allergen with monoclonal antibodies and specific IgG and IgE antibodies of the patients of aspergillosis confirmed that this protein is Asp fl.
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Affiliation(s)
- N Bir
- Centre for Biochemical Technology, Mall Road, 110007 Delhi
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30
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Kao R, Davies J. Molecular dissection of mitogillin reveals that the fungal ribotoxins are a family of natural genetically engineered ribonucleases. J Biol Chem 1999; 274:12576-82. [PMID: 10212236 DOI: 10.1074/jbc.274.18.12576] [Citation(s) in RCA: 33] [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
Mitogillin and the related fungal ribotoxins are highly specific ribonucleases which inactivate the ribosome enzymatically by cleaving the 23-28 S RNA of the large ribosomal subunit at a single phosphodiester bond. The site of cleavage occurs between G4325 and A4326 (rat ribosome numbering) which are present in one of the most conserved sequences (the alpha-sarcin loop) among the large subunit ribosomal RNAs of all living species. Amino acid sequence comparison of ribotoxins and guanyl/purine ribonucleases have identified domains or residues likely involved in ribonucleolytic activity or cleavage specificity. Fifteen deletion mutants (each 4 to 8 amino acid deletions) in motifs of mitogillin showing little amino acid sequence homology with guanyl/purine ribonucleases were constructed by site-directed mutagenesis. Analyses of the purified mutant proteins identified those regions in fungal ribotoxins contributing to ribosome targeting and modulating the catalytic activity of the toxin; some of the identified motifs are homologous to sequences in ribosomal proteins and elongation factors. This mutational study of mitogillin together with the recently published x-ray structure of restrictocin (a close relative of mitogillin) supports the hypothesis that the specific cleavage properties of ribotoxins are the result of natural genetic engineering in which the ribosomal targeting elements of ribosome-associated proteins were inserted into nonessential regions of T1-like ribonucleases.
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Affiliation(s)
- R Kao
- Department of Microbiology and Immunology, The University of British Columbia, 6174 University Blvd., Vancouver, British Columbia V6T 1Z3, Canada
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31
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Abstract
Fungal ribotoxins, such as mitogillin and the related Aspergillus toxins restrictocin and alpha-sarcin, are highly specific ribonucleases, which inactivate the ribosome enzymatically by cleaving the eukaryotic 28S RNA of the large ribosomal subunit at a single phosphodiester bond. The site of cleavage occurs between G4325 and A4326, which are present in a 14-base sequence (the alpha-sarcin loop) conserved among the large subunit rRNAs of all living species. The amino acid residues involved in the cytotoxic activities of mitogillin were investigated by introducing point mutations using hydroxylamine into a recombinant Met-mature mitogillin (mitogillin with a Met codon at the N-terminus and no leader sequence) gene constructed from an Aspergillus fumigatus cDNA clone. These constructs were cloned into a yeast expression vector under the control of the GAL1 promoter and transformed into Saccharomyces cerevisiae. Upon induction of mitogillin expression, surviving transformants revealed that substitutions of certain amino acid residues on mitogillin abolished its cytotoxicity. Non-toxic mutant genes were cloned into an Escherichia coli expression vector, the proteins overexpressed and purified to homogeneity and their activities examined by in vitro ribonucleolytic assays. These studies identified the His-49Tyr, Glu-95Lys, Arg-120Lys and His-136Tyr mutations to have a profound impact on the ribonucleolytic activities of mitogillin. We conclude that these residues are key components of the active site contributing to the catalytic activities of mitogillin.
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Affiliation(s)
- R Kao
- Department of Microbiology and Immunology, The University of British Columbia, Vancouver, Canada.
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32
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33
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Oñaderra M, Mancheño JM, Lacadena J, de los Rios V, Martínez del Pozo A, Gavilanes JG. Oligomerization of the cytotoxin alpha-sarcin associated with phospholipid membranes. Mol Membr Biol 1998; 15:141-4. [PMID: 9859111 DOI: 10.3109/09687689809074525] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
alpha-Sarcin is a cytotoxic protein that specifically inactivates ribosomes. The protein translocates across phospholipid membranes. Oligomerization of the protein occurs upon interaction with membranes. Chemically cross-linked protein oligomers have been obtained by treatment of protein-vesicle complexes with the membrane impermeant reagent bis-(sulfosuccinimidyl) suberate. These structures are only obtained in the presence of acidic lipid vesicles composed of either natural or synthetic phospholipids. Such oligomers are not produced in concentrated protein solutions in the absence of vesicles. The formation of the chemically stabilized oligomers is saturated at the same lipid to protein molar ratio as all the perturbations caused by alpha-sarcin on lipid vesicles. Results are discussed in terms of the involvement of oligomer formation on protein translocation across membranes.
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Affiliation(s)
- M Oñaderra
- Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense, Madrid, Spain.
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34
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Martínez-Ruiz A, Martínez del Pozo A, Lacadena J, Mancheño JM, Oñaderra M, López-otín C, Gavilanes JG. Secretion of recombinant pro- and mature fungal alpha-sarcin ribotoxin by the methylotrophic yeast Pichia pastoris: the Lys-Arg motif is required for maturation. Protein Expr Purif 1998; 12:315-22. [PMID: 9535698 DOI: 10.1006/prep.1997.0846] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
alpha-Sarcin is a ribosome-inactivating protein from the mold Aspergillus giganteus. The methylotrophic yeast Pichia pastoris has been transformed with two plasmids (pHILD2prealphaS and pHILS1prealphaS), which contain the complete alpha-sarcin cDNA, including its original fungal leader peptide, under the control of yeast alcohol oxidase promoter. The second one is indeed fused to the signal sequence of P. pastoris acid phosphatase. The transformed yeasts secreted both mature and pro-alpha-sarcin. The presence of this pro-alpha-sarcin in the yeast extracellular medium is due to an inefficient recognition of the pro-sequence by a putative Kex2p-like endopeptidase. A third plasmid accounting for a single mutation of the alpha-sarcin leader peptide was designed to produce a more efficient Kex2p recognition motif. This approach resulted in the extracellular production of only the mature protein, suggesting the existence of a two-step mechanism for processing its leader peptide. This recombinant alpha-sarcin is identical to the original fungal protein, according to activity and spectroscopic criteria. In addition, pro-alpha-sarcin, which has been characterized for the first time, also exhibits ribonucleolytic activity as the mature protein does. Therefore, protection of the producing cells against this kind of ribotoxins may depend on an efficient recognition of the signal sequence followed by translocation of the nascent polypeptide to the endoplasmic reticulum.
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Affiliation(s)
- A Martínez-Ruiz
- Facultad de Química, Universidad Complutense, Madrid, E-28040, Spain
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35
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Lacadena J, Martínez del Pozo A, Lacadena V, Martínez-Ruiz A, Mancheño JM, Oñaderra M, Gavilanes JG. The cytotoxin alpha-sarcin behaves as a cyclizing ribonuclease. FEBS Lett 1998; 424:46-8. [PMID: 9580156 DOI: 10.1016/s0014-5793(98)00137-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The hydrolysis of adenylyl(3'-->5')adenosine (ApA) and guanylyl(3'--> 5')adenosine (GpA) dinucleotides by the cytotoxic protein alpha-sarcin has been studied. Quantitative analysis of the reaction has been performed through reverse-phase chromatographic (HPLC) separation of the resulting products. The hydrolysis of the 3'-5' phosphodiester bond of these substrates yields the 2'-3' cyclic mononucleotide; this intermediate is converted into the corresponding 3'-monophosphate derivative as the final product of the reaction. The values of the apparent Michaelis constant (KM), kcat and kcat/KM have also been calculated. The obtained results fit into a two-step mechanism for the enzymatic activity of alpha-sarcin and allow to consider this protein as a cyclizing RNase.
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Affiliation(s)
- J Lacadena
- Departamento de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense de Madrid, Spain
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36
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Mancheño JM, Martínez del Pozo A, Albar JP, Oñaderra M, Gavilanes JG. A peptide of nine amino acid residues from alpha-sarcin cytotoxin is a membrane-perturbing structure. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 1998; 51:142-8. [PMID: 9580217 DOI: 10.1111/j.1399-3011.1998.tb00632.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
A water-soluble synthetic peptide with only nine amino acid residues, comprising the 131-139 sequence region of the cytotoxic protein alpha-sarcin (secreted by the mold Aspergillus giganteus), interacts with large unilamellar vesicles composed of acid phospholipids. It promotes lipid mixing between bilayers and leakage of vesicle aqueous contents, and it also abolishes the phospholipid phase transition. Other larger peptides containing such an amino acid sequence also produce these effects. These peptides acquire alpha-helical conformation in the presence of trifluoroethanol, but display beta-strand conformation in the presence of sodium dodecyl sulfate. The interaction of these peptides with the lipid vesicles also results in beta-structure. The obtained data are discussed in terms of the involvement of the 131-139 stretch of alpha-sarcin in its interaction with lipid membranes.
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Affiliation(s)
- J M Mancheño
- Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense, Madrid, Spain
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37
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Sylvester ID, Roberts LM, Lord JM. Characterization of prokaryotic recombinant Aspergillus ribotoxin alpha-sarcin. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1358:53-60. [PMID: 9296521 DOI: 10.1016/s0167-4889(97)00048-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The Aspergillus ribonuclease alpha-sarcin is toxic to intact mammalian cells but the mechanism by which it enters the cells to reach its ribosomal RNA substrate is unclear. Here we have compared the cytotoxicity of alpha-sarcin to that of ricin, another catalytic toxin that targets the same rRNA sequence but whose mechanism of cell entry is better understood. Intact ricin binds to cell surface components and enters the cells by receptor-mediated endocytosis, whereas the catalytic polypeptide of ricin (the A chain or RTA) which, like alpha-sarcin, is unable to bind to surface components directly and enters cells by fluid phase uptake. Recombinant alpha-sarcin was produced in Escherichia coli and purified to homogeneity. The protein was soluble, stable and its ability to inhibit in vitro protein synthesis was indistinguishable from that of native alpha-sarcin. Further, recombinant alpha-sarcin had the same in vitro protein synthesis inhibition activity as ricin A chain. The cytotoxicity of alpha-sarcin and ricin A chain to HeLa cells was also the same. The cytotoxicity of alpha-sarcin was due to its RNAase activity rather than to specific membrane effects at the cell surface, since a mutant containing a single substitution at a putative key catalytic residue had reduced ribonuclease activity and an equivalent reduction in cytotoxicity. One interpretation of the data is that a-sarcin enters mammalian cells in the same way as free ricin A chain.
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Affiliation(s)
- I D Sylvester
- Department of Biological Sciences, University of Warwick, Coventry, UK
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Desvoyes B, Poyet JL, Schlick JL, Adami P, Jouvenot M, Dulieu P. Identification of a biological inactive complex form of pokeweed antiviral protein. FEBS Lett 1997; 410:303-8. [PMID: 9237651 DOI: 10.1016/s0014-5793(97)00648-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Pokeweed antiviral protein (PAP) inactivates both eukaryotic and prokaryotic ribosomes via a specific depurination of rRNA. The sensitivity of pokeweed ribosomes to PAP implies the existence of a mechanism to protect the plant. Using monoclonal antibodies specific to PAP, a protein complex (PAPi) which contained PAP was identified in leaf extract. In this complex, the enzymatic activity of the toxin was strongly inhibited. This protein complex had a pI lower than that of PAP and was separated from free PAP by a preparative native gel electrophoresis. PAPi had an apparent molecular mass of 57 kDa and was dissociated by heating for 5 min at 80 degrees C or by treatment by alkaline or acidic pH or by 7 M urea. The other components involved in the complex remain unknown.
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Affiliation(s)
- B Desvoyes
- Laboratoire de Biochimie et Biologie Moléculaire, UFR Sciences et Techniques, Besançon, France
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Huang KC, Hwang YY, Hwu L, Lin A. Characterization of a new ribotoxin gene (c-sar) from Aspergillus clavatus. Toxicon 1997; 35:383-92. [PMID: 9080594 DOI: 10.1016/s0041-0101(96)00170-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A new ribotoxin, c-sarcin, was isolated from a culture of Aspergillus clavatus. A full-length genomic DNA (c-sar) coding for c-sarcin was cloned and sequenced. The deduced amino acid sequence showed a high homology to restrictocin and alpha-sarcin. The native toxin as well as the recombinant protein hydrolysed ribosomes and naked RNA. The genomic structure of the c-sar gene had an intron located between the coding sequences for secretory signal peptide and the mature protein. The intron contained a stretch of 38 adenines. The intron sequence of c-sar was different from that of restrictocin but resembled that of alpha-sarcin. There was 34% identity between the intron of c-sarcin and alpha-sarcin, and this similarity was further increased to 83% if the stretch of polyadenine was omitted.
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Affiliation(s)
- K C Huang
- Institute of Genetics, National Yang-Ming University, Taipei, Taiwan, R.O.C
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40
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Campos-Olivas R, Bruix M, Santoro J, Martínez del Pozo A, Lacadena J, Gavilanes JG, Rico M. Structural basis for the catalytic mechanism and substrate specificity of the ribonuclease alpha-sarcin. FEBS Lett 1996; 399:163-5. [PMID: 8980143 DOI: 10.1016/s0014-5793(96)01320-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
alpha-Sarcin is a ribosome-inactivating protein which selectively cleaves a single phosphodiester bond in a universally conserved sequence of the major rRNA. The solution structure of a-sarcin has been determined on the basis of 1898 distance and angular experimental constraints from NMR spectroscopy. It reveals a catalytic mechanism analogous to that of the T1 family of ribonucleases while its exquisite specificity resides in the contacts provided by its distinctive loops.
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Affiliation(s)
- R Campos-Olivas
- Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Científicas, Madrid, Spain
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Abstract
The substrate specificity of monomeric and dimeric forms of alpha-sarcin was investigated by membrane blotting procedures. Dimeric alpha-sarcin fails to inactivate ribosomes as well as to hydrolyze mini-stem-loop RNA, whereas monomeric alpha-sarcin catalyzes both substrates. Both monomeric and dimeric alpha-sarcin are effective ribonucleases that are displayed by in situ RNA-impregnated gel electrophoresis. The same purine base specificity was detected for both dimeric and monomeric forms. alpha-Sarcin is also an effective deoxyribonuclease to supercoiled DNA. The action of alpha-sarcin as deoxyribonuclease and ribonuclease is inhibited by the presence of SDS (3.5 x 10(-6) M); the inhibition on ribonuclease, but not on deoxyribonuclease, is reversible if the proteins are renatured.
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Affiliation(s)
- J I Cheung
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan
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42
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Campos-Olivas R, Bruix M, Santoro J, Martínez del Pozo A, Lacadena J, Gavilanes JG, Rico M. 1H and 15N nuclear magnetic resonance assignment and secondary structure of the cytotoxic ribonuclease alpha-Sarcin. Protein Sci 1996; 5:969-72. [PMID: 8732769 PMCID: PMC2143403 DOI: 10.1002/pro.5560050519] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The ribosome-inactivating protein alpha-Sarcin (alpha S) is a 150-residue fungal ribonuclease that, after entering sensitive cells, selectively cleaves a single phosphodiester bond in an universally conserved sequence of the major rRNA to inactivate the ribosome and thus exert its cytotoxic action. As a first step toward establishing the structure-dynamics-function relationships in this system, we have carried out the assignment of the 1H and 15N NMR spectrum of alpha S on the basis of homonuclear (1H-1H) and heteronuclear (1H-15N) two-dimensional correlation spectra of a uniformly 15N-labeled sample, and two selectively 15N-labeled (Tyr and Phe) samples, as well as a single three-dimensional experiment. The secondary structure of alpha S, as derived from the characteristic patterns of dipolar connectivities between backbone protons, conformational chemical shifts, and the protection of backbone amide protons against exchange, consists of a long N-terminal beta-hairpin, a short alpha-helical segment, and a C-terminal beta-sheet of five short strands arranged in a + 1, + 1, + 1, + 1 topology, connected by long loops in which the 13 Pro residues are located.
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Affiliation(s)
- R Campos-Olivas
- Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, Madrid, Spain
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Kao R, Davies J. Fungal ribotoxins: a family of naturally engineered targeted toxins? Biochem Cell Biol 1995; 73:1151-9. [PMID: 8722032 DOI: 10.1139/o95-124] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
alpha-Sarcin, mitogillin, and restrictocin are small (approximately 17 kDa) basic robosome-inactivating proteins (RIPs) produced by the Aspergilli that catalytically inactivate the large ribosomal subunits of all organisms tested to date. These three fungal ribotoxins act as specific ribonucleases by hydrolyzing one single phosphodiester bond in the universally conserved alpha-sarcin domain of 23-28S rRNAs and are among the most potent inhibitors of protein synthesis known. Previous molecular studies of ribotoxins indicated that they belong to the superfamily of ribonucleases and analysis of the mitogillin gene employing PCR-mediated site-specific mutagenesis suggests that certain domains in ribotoxins, which share homologies with motifs in ribosome-related proteins, may be responsible for the targeting of ribotoxins to the ribosome. The applications of the ribotoxins as tools in research and their uses as therapeutic and diagnostic agents are also reviewed in this paper.
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Affiliation(s)
- R Kao
- Department of Microbiology and Immunology, University of British Columbia, Vanconver, Canada
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Gasset M, Mancheño JM, Laynez J, Lacadena J, Fernández-Ballester G, Martinez del Pozo A, Oñaderra M, Gavilanes JG. Thermal unfolding of the cytotoxin alpha-sarcin: phospholipid binding induces destabilization of the protein structure. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1252:126-34. [PMID: 7548154 DOI: 10.1016/0167-4838(95)00100-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The effect of membrane binding on the structure and stability of the cytotoxin alpha-sarcin has been studied by differential scanning calorimetry, Fourier-transform infrared and fluorescence spectroscopic techniques. The thermal unfolding of alpha-sarcin in aqueous solution fits into a two-state transition characterized by a transition temperature (Tm) of 52.6 degrees C and a calorimetric enthalpy (delta Hcal) of 136 kcal/mol. Upon interaction with phosphatidylglycerol vesicles, alpha-sarcin undergoes conformational changes, as deduced from the FTIR and fluorescence emission spectra. These changes result in a decreased Tm and delta Hcal values for the thermal unfolding of phospholipid-bound alpha-sarcin. The lower Tm value for lipid-bound alpha-sarcin is also observed at the level of secondary and tertiary structures, based on analyses of both the amide I' infrared spectrum and the tryptophan emission of the protein as a function of temperature, respectively. The results obtained indicate a protein destabilization promoted by the phospholipid interaction.
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Affiliation(s)
- M Gasset
- Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense, Madrid, Spain
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Gasset M, Mancheño JM, Lacadena J, Martinez del Pozo A, Oñaderra M, Gavilanes JG. Spectroscopic characterization of the alkylated alpha-sarcin cytotoxin: analysis of the structural requirements for the protein-lipid bilayer hydrophobic interaction. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1252:43-52. [PMID: 7548165 DOI: 10.1016/0167-4838(95)00106-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
alpha-Sarcin is a ribosome-inactivating protein that translocates across lipid bilayers, these two abilities explaining its cytotoxic character. This protein is composed of a single polypeptide chain with two disulfide bridges. Reduction and carboxyamidomethylation of alpha-sarcin results in protein unfolding, based on the results of the spectroscopic characterization of the chemically modified protein. The absorption and fluorescence emission bands of the tryptophan residues of the modified protein appear blue- and red-shifted, respectively. Far-UV circular dichroism analysis reveals the presence of residual secondary structure (beta-strands and turns) in the alkylated protein. This retains its ability to interact with lipid bilayers. It promotes vesicle aggregation, lipid-mixing between bilayers and leakage of the intravesicular aqueous contents. The modified protein tends to abolish the phase transition of acid phospholipids as detected by differential scanning calorimetry and depolarization measurements of fluorescence-labelled vesicles. The protein gain access to vesicle-entrapped trypsin. The fluorescence emission of the tryptophan residues is blue-shifted upon interaction of the protein with the bilayers, and anthracene incorporated into the hydrophobic core of the membranes quenches the tryptophan fluorescence emission of the protein. The secondary structure of the alkylated protein interacting with lipid vesicles has been studied by infrared spectroscopy. An increase in the alpha-helix and turn contents and a concomitant decrease in the beta-structure content are observed upon interaction with the bilayers. The results obtained are discussed in terms of the structural requirements for the interaction of alpha-sarcin with lipid membranes.
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Affiliation(s)
- M Gasset
- Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense, Madrid, Spain
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Mazet I, Vey A. Hirsutellin A, a toxic protein produced in vitro by Hirsutella thompsonii. MICROBIOLOGY (READING, ENGLAND) 1995; 141 ( Pt 6):1343-1348. [PMID: 7670635 DOI: 10.1099/13500872-141-6-1343] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A toxic protein, hirsutellin A, has been purified from the mite fungal pathogen, Hirsutella thompsonii, using ammonium sulphate precipitation, ion exchange chromatography and gel filtration on Bio-Gel P-10. The protein has been characterized as a monomer with a molecular mass of 15 kDa and an isoelectric point of 10.5. The amino acid composition and the N-terminal sequence of hirsutellin A (34 amino acids) have been determined. From these results, the toxin appears to be distinct from other known proteins. It is not glycosylated, and does not show proteolytic activity. The toxin is also antigenic, thermostable and not inactivated by treatments with proteolytic enzymes. Toxicity bioassays showed that injection of larvae of the waxmoth, Galleria mellonella, with hirsutellin A at low dosages [1 microgr toxin (g body wt)-1] caused a high mortality rate. Hirsutellin A was also toxic per os to neonatal larvae of the mosquito Aedes aegypti.
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Affiliation(s)
- Isabelle Mazet
- Station de Recherches de Pathologie Compare INRA-CNRS, 30380 Saint-Christol-Lez-Als, France
| | - Alain Vey
- Station de Recherches de Pathologie Compare INRA-CNRS, 30380 Saint-Christol-Lez-Als, France
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Lin A, Huang KC, Hwu L, Tzean SS. Production of type II ribotoxins by Aspergillus species and related fungi in Taiwan. Toxicon 1995; 33:105-10. [PMID: 7778122 DOI: 10.1016/0041-0101(94)00140-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A molecular investigation was conducted on the production of type II ribotoxin of the species Aspergillus and related fungi in Taiwan. Species that carried ribotoxin were confirmed by (1) cross-reactivity to anti-alpha-sarcin serum; (2) Southern dot hybridization; (3) PCR amplification of genomic DNA with specific primers; and (4) analysis of ribotoxic activity. Five new strains, A. clavatus, A. oryzae var. effusus, A. ostianus, A. tamarii, and Neosartorya fischeri var. spinosa, were identified to contain an alpha-sarcin-like ribotoxin. These positive strains exhibit ribotoxic activity by cleaving ribosomes and generating an alpha-fragment.
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Affiliation(s)
- A Lin
- Institute of Genetics, National Yang-Ming Medical College, Taipei, Taiwan, R.O.C
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48
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Turnay J, Olmo N, Jiménez A, Lizarbe MA, Gavilanes JG. Kinetic study of the cytotoxic effect of alpha-sarcin, a ribosome inactivating protein from Aspergillus giganteus, on tumour cell lines: protein biosynthesis inhibition and cell binding. Mol Cell Biochem 1993; 122:39-47. [PMID: 8350862 DOI: 10.1007/bf00925735] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
alpha-Sarcin is a ribosome inactivating protein produced by the mould Aspergillus giganteus. The effect of this protein on eight different tumour cell lines has been studied in the absence of any agent affecting membrane permeability. The protein is cytotoxic for all the tumour cell lines considered. alpha-Sarcin modifies the cell proliferation pattern by inhibiting the protein biosynthesis of the cultured cells. No membrane damage produced by alpha-sarcin has been observed by measuring lactic dehydrogenase leakage. Alteration on the cell mitochondrial activity has not been detected upon treatment with alpha-sarcin. Differences on the extent of the protein binding to the cells have been observed by flow cytometric measurements. The kinetic analysis of the protein biosynthesis inhibition produced by alpha-sarcin reveals an alpha-sarcin concentration-dependent lag phase followed by a first order decrease of the protein synthesis rate. This parameter is dependent on the external alpha-sarcin concentration. A saturable component for the action of alpha-sarcin is also deduced from these experiments. Results are discussed in terms of the protein passage across the cell membrane as the potential rate-limiting step for the action of alpha-sarcin.
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Affiliation(s)
- J Turnay
- Department of Biochemistry and Molecular Biology, Faculty of Sciences, Complutense University, Madrid, Spain
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49
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Wnendt S, Felske-Zech H, Henze PP, Ulbrich N, Stahl U. Characterization of the gene encoding alpha-sarcin, a ribosome-inactivating protein secreted by Aspergillus giganteus. Gene X 1993; 124:239-44. [PMID: 8444347 DOI: 10.1016/0378-1119(93)90399-n] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The filamentous fungus, Aspergillus giganteus, produces the extracellular ribosome-inactivating protein, alpha-sarcin (Sar). The structural gene (sar) encoding Sar was isolated and characterized by sequence analysis and expression in Aspergillus niger. It codes for a precursor of 177 amino acids containing a secretion signal sequence that is absent in the mature protein. The nucleotide sequence contains several typical features of fungal genes, including a short intron of 65 bp. The transcriptional and translational processing signals of the gene are functional in A. niger, but the yield of recombinant protein is low in comparison with the natural producer. A comparison of sar with the gene encoding restrictocin from Aspergillus restrictus revealed a high degree of similarity between both genes. The conservation of the aa sequence suggests that Sar-like proteins may confer a selective advantage to these fungi under certain environmental conditions.
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Affiliation(s)
- S Wnendt
- Berlin University of Technology, Department of Microbiology and Genetics, Germany
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50
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Glück A, Endo Y, Wool IG. Ribosomal RNA identity elements for ricin A-chain recognition and catalysis. Analysis with tetraloop mutants. J Mol Biol 1992; 226:411-24. [PMID: 1379305 DOI: 10.1016/0022-2836(92)90956-k] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Ricin is a cytotoxic protein that inactivates ribosomes by hydrolyzing the N-glycosidic bond between the base and the ribose of the adenosine at position 4324 in eukaryotic 28 S rRNA. Ricin A-chain will also catalyze depurination in naked prokaryotic 16 S rRNA; the adenosine is at position 1014 in a GAGA tetraloop. The rRNA identity elements for recognition by ricin A-chain and for the catalysis of cleavage were examined using synthetic GAGA tetraloop oligoribonucleotides. The RNA designated wild-type, an oligoribonucleotide (19-mer) that approximates the structure of the ricin-sensitive site in 16 S rRNA, and a number of mutants were transcribed in vitro from synthetic DNA templates with phage T7 RNA polymerase. With the wild-type tetraloop oligoribonucleotide the ricin A-chain-catalyzed reaction has a Km of 5.7 microM and a Kcat of 0.01 min-1. The toxin alpha-sarcin, which cleaves the phosphodiester bond on the 3' side of G4325 in 28 S rRNA, does not recognize the tetraloop RNA, although alpha-sarcin does affect a larger synthetic oligoribonucleotide that has a 17-nucleotide loop with a GAGA sequence; thus, there is a clear divergence in the identity elements for the two toxins. Mutants were constructed with all of the possible transitions and transversions of each nucleotide in the GAGA tetraloop; none was recognized by ricin A-chain. Thus, there is an absolute requirement for the integrity of the GAGA sequence in the tetraloop. The helical stem of the tetraloop oligoribonucleotide can be reduced to three base-pairs, indeed, to two base-pairs if the temperature is decreased, without affecting recognition; the nature of these base-pairs does not influence recognition or catalysis by ricin A-chain. If the tetraloop is opened so as to form a GAGA-containing hexaloop, recognition by ricin A-chain is lost. This suggests that during the elongation cycle, a GAGA tetraloop either exists or is formed in the putative 17-member single-stranded region of the ricin domain in 28 S rRNA and this bears on the mechanism of protein synthesis.
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MESH Headings
- Base Sequence
- Endoribonucleases
- Escherichia coli
- Fungal Proteins/pharmacology
- Kinetics
- Molecular Sequence Data
- Nucleic Acid Conformation
- Oligonucleotides/metabolism
- RNA, Bacterial/metabolism
- RNA, Bacterial/ultrastructure
- RNA, Ribosomal, 16S/metabolism
- RNA, Ribosomal, 16S/ultrastructure
- RNA, Ribosomal, 28S/metabolism
- RNA, Ribosomal, 28S/ultrastructure
- Ricin/metabolism
- Structure-Activity Relationship
- Substrate Specificity
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Affiliation(s)
- A Glück
- Department of Biochemistry and Molecular Biology, University of Chicago, IL 60637
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