scholarly journals Incorporation of GP64 into Helicoverpa armigera nucleopolyhedrovirus enhances virus infectivity in vivo and in vitro

2012 ◽  
Vol 93 (12) ◽  
pp. 2705-2711 ◽  
Author(s):  
Shu Shen ◽  
Yinyin Gan ◽  
Manli Wang ◽  
Zhihong Hu ◽  
Hualin Wang ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Helicoverpa Armigera ◽  
Fusion Proteins ◽  
Virus Infectivity ◽  
F Protein ◽  
Recombinant Viruses ◽  
Group I ◽  
Helicoverpa Armígera

The envelope fusion proteins of baculoviruses, glycoprotein GP64 from group I nucleopolyhedrovirus (NPV) or the F protein from group II NPV and granulovirus, are essential for baculovirus morphogenesis and infectivity. The F protein is considered the ancestral baculovirus envelope fusion protein, while GP64 is a more recent evolutionary introduction into baculoviruses and exhibits higher fusogenic activity than the F protein. Each of the fusion proteins is required by the respective virus to spread infection within larval tissues. A recombinant Helicoverpa armigera NPV (HearNPV) expressing GP64 from Autographa californica multiple nucleopolyhedrovirus, vHaBac-gp64-egfp, was constructed, which still retained the native F protein, and its infectivity was assayed in vivo and in vitro. Analyses by one-step growth curve to determine viral titre and by quantitative PCR to determine viral DNA copy number showed that vHaBac-gp64-egfp was more infectious in vitro than the control, vHaBac-egfp. The polyhedrin gene (polh) was reintroduced into the recombinant viruses and bioassays showed that vHaBac-gp64-polh accelerated the mortality of infected larvae compared with the vHaBac-egfp-polh control, and the LC50 (median lethal concentration) of vHaBac-gp64-polh was reduced to approximately 20 % of that of vHaBac-egfp-polh. Therefore, incorporation of GP64 into HearNPV budded virions improved virus infectivity both in vivo and in vitro. The construction of this bivalent virus with a more efficient fusion protein could improve the use of baculoviruses in different areas such as gene therapy and biocontrol.

scholarly journals Potensi Nematoda Patogen Serangga Steinernema spp. dalam Pengendalian Hama Utama Tanaman Kapas

2016 ◽  
Vol 1 (2) ◽  
pp. 101
Author(s):  
Heri Prabowo ◽  
I.G.A.A. Indrayani
Keyword(s):  
Helicoverpa Armigera ◽  
Insect Pests ◽  
Soil Surface ◽  
Tenebrio Molitor ◽  
Pectinophora Gossypiella ◽  
Helicoverpa Armígera ◽  
Soy Bean Oil

<p>Steinernema spp. memiliki potensi untuk mengendalikan hama tanaman kapas seperti Helicoverpa armigera dan Pectinophora gossypiella. Steinernema spp. mampu menyebabkan mortalitas P. gossypiella dan H. armi-gera berturut-turut sebesar 31,6–55,4 dan 46,3–63,8%. Steinernema spp. memiliki kemampuan membunuh lebih baik pada P. gossypiella, sedangkan kemampuan reproduksi dalam inangnya lebih baik pada H. armi-gera. Steinernema spp. mampu menginfeksi serangga inang lebih baik pada stadium ulat lebih tua diban-dingkan stadium muda. Steinernema spp. dapat diproduksi secara in vivo dan in vitro. Produksi secara in vivo dapat menggunakan Tenebrio molitor, Tirathaba rufivena, dan Attacus atlas. Produksi secara in vitro dapat menggunakan usus ayam, lemak sapi, dan minyak kedelai. Perlu dikembangkan formulasi Steinerne-ma spp. yang murah dan efektif untuk mengendalikan hama di atas permukaan tanah. Selain itu diperlukan pencarian isolat Steinernema spp. yang virulen dan cepat membunuh hama sasaran.</p><p> </p><p>Steinernema spp. could be potentially used for controlling H. armigera and P. gossypiella on cotton. Steiner-nema spp. causes mortality on P. gossypiella and H. armigera 31,6–55,4 and 46,3–63,8% respectively. The nematode causes a higher mortality on P. gossypiella than on H. armigera, however, produces more juvenile infective on H. armigera than on P. gossypiella. Higher successful infections of Steinernema spp. occurs on late larval stadium than on early one. Production of Steinernema spp. can be in vivo using Tenebrio molitor, Tirathaba rufivena, and Attacus atlas; and in vitro using chicken intestinum, cow lipid, and soy bean oil. For effecttively use, this nematode need to be formulated especially for controlling insect pests on soil surface, as well as finding the more virulent isolates against the target insects.</p>

In Silico and in Vivo Investigations of Bioagent Helicoverpa Nucleopolyhedrovirus against Helicoverpa armigera in Chickpea

2021 ◽  
Vol 9 (2) ◽  
pp. 21-32
Author(s):  
Ritu Srivastava ◽  
◽  
Amritesh Chandra Shukla ◽  
Keyword(s):  
Green Tea ◽  
Rice Bran ◽  
Helicoverpa Armigera ◽  
Maximum Yield ◽  
3D Structure ◽  
Homology Model ◽  
In Vitro Toxicity ◽  
Helicoverpa Armígera

During investigations; homology model of 3D-structure was built for sequence of polyhedrin protein of Helicoverpa armigera nucleopolyhedrovirus, containing 246 amino acids (Accession: ACI05106.1 GI: 205946055), and evaluated through multiple tools/ applications to judge extent of accuracy in light of existing crystal structure. Further, in vivo experiments were conducted and determined response of different adjuvants with HaNPV and their efficacy. The pooled mean mortality of larvae exposed to virus mixed with 5% green tea and 5% rice bran filtrates (8.3 larvae per 25 plants) was differ significantly from control (15.8 larvae per 25 plants), suggesting that UV protectants & diet enhancer (mannitol) has ability to protect stability of virulence of the virus, under field conditions. The minimum percent pod damage of 8.6% and maximum yield of 1604.8 Kg ha-1 at harvesting was recorded with formulation of indigenous BHA virus isolate @ 2.2 x 105 POBs mL-1 mixed with Roket @50 ppm; followed by formulation with mannitol (@ 1% + green tea 5% + 5% rice bran filtrates) with percent pod damage of 16.8 % and yield of 1045.8 Kg ha-1 of chickpea. Furthermore, in vitro toxicity of fresh virus suspension @ 250 mL ha-1 was recorded more toxic in terms of percent mortality and LT50 (5.65 days). However, three months stored HaNPV formulations [(A) mannitol @ 1%+ green tea@ 5% and (B) mannitol @ 1% + green tea 5% + 5% rice bran filtrates] were more effective in larval reduction with LT50 of 7.89 and 6.00 days, respectively. Virus mixed with 5% green tea and 5% rice bran filtrates gave stability to formulation up-to one year with LT50 of 7.64 days. Findings showed that HaNPV formulations with mannitol (B) have potential that can be used in integrated manner with other IPM practices, to reduce the use of toxic synthetic pesticides in chickpea.

scholarly journals The F-Like Protein Ac23 Enhances the Infectivity of the Budded Virus of gp64-Null Autographa californica Multinucleocapsid Nucleopolyhedrovirus Pseudotyped with Baculovirus Envelope Fusion Protein F

2008 ◽  
Vol 82 (19) ◽  
pp. 9800-9804 ◽  
Author(s):  
Manli Wang ◽  
Ying Tan ◽  
Feifei Yin ◽  
Fei Deng ◽  
Just M. Vlak ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Fusion Proteins ◽  
Spodoptera Exigua ◽  
Autographa Californica ◽  
Pseudotyped Virus ◽  
F Protein ◽  
Group I ◽  
Protein F ◽  
Budded Virus ◽  
Functional Envelope

ABSTRACT The GP64 and F proteins were previously identified as the sole functional envelope fusion proteins in Baculoviridae. F-like proteins, present only in group I nucleopolyhedroviruses (NPVs), are remnant, nonfunctional F proteins. In this report, we describe the effect of the presence or absence of the F-like protein Ac23 in a gp64-null Autographa californica multinucleocapsid NPV pseudotyped with the F protein from Spodoptera exigua multicapsid NPV (SeF). We found that the presence of Ac23 elevates the infectivity of the pseudotyped virus. This is in contrast to the results of Lung et al. (J. Virol. 76:5729-5736, 2002), who found no such effect. The possible reasons for the differing results are discussed.

scholarly journals Function, oligomerization and N-linked glycosylation of the Helicoverpa armigera single nucleopolyhedrovirus envelope fusion protein

2006 ◽  
Vol 87 (4) ◽  
pp. 839-846 ◽  
Author(s):  
Gang Long ◽  
Marcel Westenberg ◽  
Hualin Wang ◽  
Just M. Vlak ◽  
Zhihong Hu
Keyword(s):  
Fusion Protein ◽  
Helicoverpa Armigera ◽  
Disulfide Bonds ◽  
Attractive Alternative ◽  
Present Observation ◽  
Reading Frame ◽  
Group I ◽  
The Family ◽  
Helicoverpa Armígera ◽  
Group Ii

In the family Baculoviridae, two distinct envelope fusion proteins are identified in budded virions (BVs). GP64 is the major envelope fusion protein of group I nucleopolyhedrovirus (NPV) BVs. An unrelated type of envelope fusion protein, named F, is encoded by group II NPVs. The genome of Helicoverpa armigera (Hear) NPV, a group II NPV of the single nucleocapsid or S type, also encodes an F-like protein: open reading frame 133 (Ha133). It was demonstrated by N-terminal sequencing of the major 59 kDa protein present in HearNPV BV that this protein is one of the two F subunits: F1 (transmembrane subunit of 59 kDa) and F2 (surface subunit of 20 kDa), both the result of cleavage by a proprotein convertase and disulfide-linked. The HearNPV F protein proved to be a functional analogue of GP64, as the infectivity of an AcMNPV gp64-deletion mutant was rescued by the introduction of the HearNPV F gene. It was also demonstrated by chemical cross-linking that HearNPV F is present in BVs as an oligomer whereby, unlike GP64, disulfide bonds are not involved. Deglycosylation assays indicated that both F1 and F2 possess N-linked glycans. However, when F was made in Hz2E5 cells, these glycans did not have an α-1-3 core fucose modification that usually occurs in insect cells. As α-1-3 core fucose is a major inducer of an allergic response in humans, the present observation makes the HearNPV–Hz2E5 system an attractive alternative for the production of recombinant glycoproteins for therapeutic use in humans.

Preclinical Research on Idiotype Vaccine Against B Cell Lymphoma.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 4744-4744
Author(s):  
Fuxu Wang ◽  
Bing Zhao ◽  
Ling Pan ◽  
Xuejun Zhang ◽  
Jianmin Luo ◽  
...  
Keyword(s):  
Fusion Protein ◽  
B Cell ◽  
Fusion Proteins ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Host Cells ◽  
Fusion Genes ◽  
Preclinical Research

Abstract The idiotype (Id) of immunoglobulin expressed by B cell lymphoma can serve as the only widely accepted tumor associated antigen. But the Id vaccines have failed to elicit anti-tumor immunity for its weak immunogenic. Monocyte chemoattractant protein-3 (MCP3) can recruit various subsets of immune cells, such as DCs, which would uptake and properly process and present Id, activating both arms of the immune system, humoral and cellular. So the Id-MCP3 fusion proteins are potential vaccines for immunotherapy of B cell lymphoma. In this study, two vaccine candidates were constructed by fusing allogeneous MCP3 to the amino-(MCP3-scFv) or carboxyl-(scFv-MCP3) terminus of the A20 (BABL/c murine B-lymphocyte) Id scFv with a flexible polypeptide spacer encoding NDAQAPKS to prevent dissociation and keep their respective natural construction and function. And VH and VL domains were linked with a current linker encoding (Gly4Ser)3. Firstly, the cDNAs of Ig VH and Ig VL were amplified by RT-PCR from A20 mRNA, and then assembled into scFv by recombinant PCR method. Secondly the fusion genes of scFv/MCP3 were formed using the same method. After sequencing, MCP3/scFv fusion genes were cloned into pET-39b vector. Lastly MCP3/scFv fusion proteins were expressed in E.coli BL21. And the fusion protein is about 62 kD. We found that, under the same condition, MCP3-scFv fusion protein was expressed successfully and accounted for 40% of the total protein of the bacteria but not scFv-MCP3. Our result indicated that fusing MCP3 to carboxyl-terminus of scFv protein may have cytotoxicity to the host cells or maybe not stable inside the host cells. Next we will determine the activity of the fusion protein MCP3-scFv with cell-chemotatic-experiment in vitro and bearing-tumor mice experiment in vivo. Once the results would suggest that there may be an anti-tumor effect, we can make individual vaccines to lead to a better survival.

Blockade Of CD47 Using SIRPαFc: Role Of The Fc Region In Anti-Leukemic Activity and Tolerability

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3935-3935 ◽  
Author(s):  
Robert A. Uger ◽  
Xinli Pang ◽  
Mark Wong ◽  
Violetta House ◽  
Karen Dodge ◽  
...  
Keyword(s):  
Stem Cell ◽  
Fusion Protein ◽  
Fusion Proteins ◽  
Research Funding ◽  
Cell Therapeutics ◽  
Human Igg1 ◽  
Effector Activity ◽  
Stem Cell Therapeutics

Abstract Introduction CD47 binds to SIRPα on the surface of macrophages and delivers a “do not eat” signal that suppresses phagocytosis. There is increasing evidence that acute myeloid leukemia (AML) stem cells exploit the CD47-SIRPα pathway to escape macrophage-mediated destruction. Blockade of CD47 using a soluble SIRPα-Fc fusion protein (SIRPαFc) has emerged as a promising strategy to neutralize the suppressive effects of CD47 and promote the eradication of AML cells. However, little information is available regarding the optimal structure of SIRPαFc. In particular, the influence of the Fc region, which can mediate antibody-dependent cellular cytotoxicity and complement activation, on anti-leukemic activity and toxicity has not been explored. Results We have generated three unique human SIRPαFc fusion proteins that vary in their Fc regions: SIRPα-G1, which contains the Fc region from human IgG1 with full effector activity; SIRPα-G4, bearing the Fc region from human IgG4, which has low effector activity; and SIRPα-G4m, which possesses a mutated human IgG4 Fc region that is devoid of any effector activity. These three fusion proteins were tested for their ability to promote macrophage-mediated phagocytosis of patient-derived AML cells in vitro. Although all three proteins were able to stimulate tumor cell destruction, SIRPα-G4m was clearly the least potent, while SIRPα-G1 and SIRPα-G4 showed similar activity. Next, the anti-leukemic activity of the fusion proteins was assessed in an AML xenograft model in NOD.SCID mice. SIRPα-G1 induced a profound anti-leukemic effect and was superior to both SIRPα-G4 and SIRPα-G4m, particularly with respect to eradicating tumor cells within the transplanted femur. Thus, while only a low level of Fc activity was required for maximal pro-phagocytic activity in vitro, full effector activity (human IgG1) provided superior anti-leukemic activity in vivo. The strong anti-tumor activity of this fusion protein presumably results from the simultaneous delivery of a positive macrophage activating signal (through Fc receptors) and blockade of the negative “do not eat” signal from CD47. Increased Fc effector activity could also carry the risk of increased toxicity. Since human SIRPα has no measurable binding to mouse CD47, to assess tolerability in mice we generated a surrogate fusion protein consisting of NOD mouse SIRPα linked to a mouse IgG2a Fc region with full effector function (mSIRPα-G2a). Repeat administration of high dose mSIRPα-G2a to mice (50 mg/kg IP twice per week for 8 weeks) produced no adverse clinical effects. No abnormalities were observed in hematological parameters, (including erythrocyte, platelet and leukocyte counts) or bone marrow CD150+CD48- LSK hematopoietic stem cells, nor were gross or microscopic changes noted in any tissue. Furthermore, taking advantage of a fortuitous cross-reactivity between NOD SIRPα and human CD47, we conducted a xenograft study with patient-derived AML cells using the mSIRPα-G2a fusion protein. Compared to control Fc, mSIRPα-G2a profoundly reduced leukemic burden in both the injected femur and non-injected bone marrow at doses significantly below the 50 mg/kg used in the tolerability studies. Thus, a mouse surrogate fusion that can bind both human CD47 on xenograft AML cells and endogenous CD47 on host tissue is both safe and effective. A pilot repeat-dose toxicity study using various human SIRPαFc proteins is currently underway in non-human primates. Conclusions These results demonstrate that SIRPαFc fusion proteins that combine Fc activity with CD47 blockade lead to effective AML destruction in vitro and in vivo, and are well tolerated in mice. Thus the therapeutic window in a homologous model system appears to be sufficiently wide to proceed with formal IND-enabling studies. On the basis of these findings we are moving forward with the development of a SIRPαFc therapeutic for the treatment of AML. Disclosures: Uger: Trillium Therapeutics/Stem Cell Therapeutics: Employment. Pang:Trillium Therapeutics/Stem Cell Therapeutics: Employment. Wong:Trillium Therapeutics/Stem Cell Therapeutics: Employment. House:Trillium Therapeutics/Stem Cell Therapeutics: Employment. Dodge:Trillium Therapeutics/Stem Cell Therapeutics: Employment. Viau:Trillium Therapeutics/Stem Cell Therapeutics: Employment. Vigo:Trillium Therapeutics/Stem Cell Therapeutics: Employment. Tam:Trillium Therapeutics/Stem Cell Therapeutics: Employment. Truong:Trillium Therapeutics/Stem Cell Therapeutics: Employment. Jin:Trillium Therapeutics/Stem Cell Therapeutics: Research Funding. Malko:Trillium Therapeutics/Stem Cell Therapeutics: Research Funding. Ho:Trillium Therapeutics/Stem Cell Therapeutics: Research Funding. Prasolava:Trillium Therapeutics/Stem Cell Therapeutics: Research Funding. Danska:Trillium Therapeutics/Stem Cell Therapeutics: Research Funding. Wang:Trillium Therapeutics/Stem Cell Therapeutics: Research Funding. Petrova:Trillium Therapeutics/Stem Cell Therapeutics: Employment.

scholarly journals Bombyx mori nucleopolyhedrovirus SNF2 global transactivator homologue (Bm33) enhances viral pathogenicity in B. mori larvae

2008 ◽  
Vol 89 (12) ◽  
pp. 3039-3046 ◽  
Author(s):  
Susumu Katsuma ◽  
Tsuguru Fujii ◽  
Shinpei Kawaoka ◽  
Toru Shimada
Keyword(s):  
Bombyx Mori ◽  
Early Gene ◽  
Transcriptional Analysis ◽  
Virus Infectivity ◽  
Wild Type ◽  
Virus Growth ◽  
Group I ◽  
Bmn Cells

The SNF2 global transactivator gene homologue (Bm33) of Bombyx mori nucleopolyhedrovirus (BmNPV) is one of the genes exclusive to group I NPVs, but its function remains unknown. This study describes the characterization of Bm33. Transcriptional analysis suggested that Bm33 is an early gene, as its transcript was observed at 4 h post-infection in BmNPV-infected BmN cells. To examine the role of Bm33 during BmNPV infection, a Bm33 deletion mutant (BmORF33D) was constructed and its infectivity was characterized in BmN cells and B. mori larvae. BmORF33D did not have any obvious defects in the production of budded viruses (BVs) or occlusion bodies (OBs) in BmN cells compared with wild-type BmNPV. Larval bioassays revealed that deletion of Bm33 did not reduce virus infectivity. However, BmORF33D took approximately 10–15 h longer than wild-type BmNPV to kill B. mori larvae when tested by either BV injection or OB ingestion. These results suggest that Bm33 is not essential for virus growth in vitro or in vivo, but that it accelerates the time of death of B. mori larvae.

Effects of dietary quercetin on performance and cytochrome P450 expression of the cotton bollworm, Helicoverpa armigera

2015 ◽  
Vol 105 (6) ◽  
pp. 771-777 ◽  
Author(s):  
D. Liu ◽  
Y. Yuan ◽  
M. Li ◽  
X. Qiu
Keyword(s):  
Cytochrome P450 ◽  
Helicoverpa Armigera ◽  
Adult Emergence ◽  
Cotton Bollworm ◽  
Molecular Response ◽  
Terrestrial Plants ◽  
P450 Expression ◽  
Helicoverpa Armígera

AbstractQuercetin is ubiquitous in terrestrial plants. The cotton bollworm Helicoverpa armigera as a highly polyphagous insect has caused severe crop losses. Until now, interactions between this pest and quercetin are poorly understood at the biochemical and molecular levels. In this study, we investigated the in vivo effects of quercetin on performance of cotton bollworm and on cytochrome P450 (P450) expression. Deleterious effects of quercetin on the performance of the cotton bollworm, including growth, survival, pupation and adult emergence were observed after oral administration of 3 and 10 mg g−1 quercetin to larvae since the third instar, whereas no significant toxic effect was found at 0.1 mg g−1 quercetin treatment. Piperonyl butoxide treatment enhanced the toxicity of quercetin. In vitro metabolism studies showed that quercetin was rapidly transformed by gut enzymes of fifth instar larvae of the cotton bollworm. qRT–PCR results revealed that the effect of quercetin on P450 expression was tissue- and dose-specific. Quercetin regulated P450 expression in a mild manner, and it could serve as P450 inducer (CYP337B1, CYP6B6) or repressor (CYP337B1, CYP6B7, CYP6B27, CYP9A14, CYP6AE11, and CYP4M7). These findings are important for advancing our understanding of the biochemical and molecular response of insects to plant toxins and have implications for a smart pest control.

scholarly journals New Resistance Mechanism in Helicoverpa armigera Threatens Transgenic Crops Expressing Bacillus thuringiensis Cry1Ac Toxin

2005 ◽  
Vol 71 (5) ◽  
pp. 2558-2563 ◽  
Author(s):  
Robin V. Gunning ◽  
Ho T. Dang ◽  
Fred C. Kemp ◽  
Ian C. Nicholson ◽  
Graham D. Moores
Keyword(s):  
Bacillus Thuringiensis ◽  
Helicoverpa Armigera ◽  
Resistance Mechanism ◽  
Transgenic Cotton ◽  
In Vivo Studies ◽  
Cry1ac Toxin ◽  
Helicoverpa Armígera ◽  
History Of

ABSTRACT In Australia, the cotton bollworm, Helicoverpa armigera, has a long history of resistance to conventional insecticides. Transgenic cotton (expressing the Bacillus thuringiensis toxin Cry1Ac) has been grown for H. armigera control since 1996. It is demonstrated here that a population of Australian H. armigera has developed resistance to Cry1Ac toxin (275-fold). Some 70% of resistant H. armigera larvae were able to survive on Cry1Ac transgenic cotton (Ingard) The resistance phenotype is inherited as an autosomal semidominant trait. Resistance was associated with elevated esterase levels, which cosegregated with resistance. In vitro studies employing surface plasmon resonance technology and other biochemical techniques demonstrated that resistant strain esterase could bind to Cry1Ac protoxin and activated toxin. In vivo studies showed that Cry1Ac-resistant larvae fed Cy1Ac transgenic cotton or Cry1Ac-treated artificial diet had lower esterase activity than non-Cry1Ac-fed larvae. A resistance mechanism in which esterase sequesters Cry1Ac is proposed.

scholarly journals Activation Process of Dipteran-Specific Insecticidal Protein Produced by Bacillus thuringiensissubsp. israelensis

1999 ◽  
Vol 65 (8) ◽  
pp. 3464-3469 ◽  
Author(s):  
Masashi Yamagiwa ◽  
Motoyuki Esaki ◽  
Kanao Otake ◽  
Manabu Inagaki ◽  
Tohru Komano ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Fusion Proteins ◽  
Culex Pipiens ◽  
Insecticidal Protein ◽  
Activation Process ◽  
Mosquito Larvae ◽  
In Vitro Processing ◽  
Significant Toxicity

ABSTRACT Dipteran-specific insecticidal protein Cry4A is produced as a protoxin of 130 kDa in Bacillus thuringiensis subsp.israelensis. Here we performed the in vitro processing of Cry4A and showed that the 130-kDa protoxin of Cry4A was processed into the two protease-resistant fragments of 20 and 45 kDa through the intramolecular cleavage of a 60-kDa intermediate. The processing into these two fragments was also observed in vivo. To investigate functional properties of the two fragments, GST (glutathioneS-transferase) fusion proteins of the 60-kDa intermediate and the 20- and 45-kDa fragments were constructed. Neither the GST–20-kDa fusion protein (GST-20) nor the GST–45-kDa fusion protein (GST-45) was actively toxic against mosquito larvae of Culex pipiens, whereas the GST–60-kDa intermediate fusion protein (GST-60) exhibited significant toxicity. However, when the two fusion proteins GST-20 and GST-45 coexisted, significant toxicity was observed. The coprecipitation experiment demonstrated that the two fragments associated with each other. Therefore, it is strongly suggested that the two fragments formed an active complex of apparently 60 kDa. A mutant of the 60-kDa protein which was apparently resistant to the intramolecular cleavage with the midgut extract of C. pipiens larvae had toxicity slightly lower than that of GST-60.

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