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Delta endotoxins

April 11, 2024

Delta endotoxins (δ-endotoxins) are a family of pore-forming toxins produced by Bacillus thuringiensis species of bacteria. They are useful for their insecticidal action and are the primary toxin produced by the genetically modified (GM) Bt maize/corn and other GM crops. During spore formation the bacteria produce crystals of such proteins (hence the name Cry toxins) that are also known as parasporal bodies, next to the endospores; as a result some members are known as a parasporin. The Cyt (cytolytic) toxin group is another group of delta-endotoxins formed in the cytoplasm. VIP toxins (vegetative insecticidal proteins) are formed at other stages of the life cycle.[2]

Delta endotoxin, N-terminal domain
crystal structure of the insecticidal bacterial del endotoxin Cry3Bb1 Bacillus thuringiensis[1]
Identifiers
SymbolEndotoxin_N
PfamPF03945
InterProIPR005639
SCOP21dlc / SCOPe / SUPFAM
TCDB1.C.2
Available protein structures:
Pfam  structures / ECOD  
PDBRCSB PDB; PDBe; PDBj
PDBsumstructure summary
Delta endotoxin, middle domain
Identifiers
SymbolEndotoxin_M
PfamPF00555
Pfam clanCL0568
InterProIPR015790
SCOP21dlc / SCOPe / SUPFAM
TCDB1.C.2
Available protein structures:
Pfam  structures / ECOD  
PDBRCSB PDB; PDBe; PDBj
PDBsumstructure summary
Delta endotoxin, middle domain, Cry2A and Cry18
insecticidal crystal protein cry2aa
Identifiers
SymbolEndotoxin_mid
PfamPF09131
InterProIPR015214
SCOP21i5p / SCOPe / SUPFAM
Available protein structures:
Pfam  structures / ECOD  
PDBRCSB PDB; PDBe; PDBj
PDBsumstructure summary
Delta endotoxin, C-terminal
Identifiers
SymbolEndotoxin_C
PfamPF03944
Pfam clanCL0202
InterProIPR005638
SCOP21dlc / SCOPe / SUPFAM
TCDB1.C.2
CDDcd04085
Available protein structures:
Pfam  structures / ECOD  
PDBRCSB PDB; PDBe; PDBj
PDBsumstructure summary
Cytolytic delta-endotoxin Cyt1/2
Identifiers
SymbolCytB
PfamPF01338
InterProIPR001615
SCOP21cby / SCOPe / SUPFAM
TCDB1.C.71
Available protein structures:
Pfam  structures / ECOD  
PDBRCSB PDB; PDBe; PDBj
PDBsumstructure summary

Mechanism of action edit

When an insect ingests these proteins, they are activated by proteolytic cleavage. The N-terminus is cleaved in all of the proteins and a C-terminal extension is cleaved in some members. Once activated, the endotoxin binds to the gut epithelium and causes cell lysis by the formation of cation-selective channels, which leads to death.[3][1]

For many years there was no clarity as to the relationship between aminopeptidase N and Bt toxins. Although AP-N does bind Cry proteins in vitro[4] (reviewed by Soberón et al. 2009[5] and Pigott & Ellar 2007[6]),[7] no cases of resistance – or even reduced in vitro binding – due to AP-N structure alteration were known through 2002, and there was some doubt that the resistance mechanism was so straight forward. Indeed, Luo et al. 1997, Mohammed et al. 1996, and Zhu et al. 2000 positively found this to not occur in Lepidoptera examples.[4] Subsequently, however Herrero et al. 2005 showed correlation between nonexpression and Bt resistance,[7] and actual resistance was found in Helicoverpa armigera by Zhang et al. 2009,[7][8] in Ostrinia nubilalis by Khajuria et al. 2011, and in Trichoplusia ni by Baxter et al. 2011 and Tiewsiri & Wang 2011 (also all Lepidoptera).[7] There continues to be confirmation that AP-Ns do not by themselves affect resistance in some cases, possibly due to sequential binding by the toxin being required to produce its effect. In this sequence each binding step is theoretically not indispensable, but if it occurs does contribute to the final pore formation result.[8]

Structure edit

The activated region of the delta toxin is composed of three distinct structural domains: an N-terminal helical bundle domain (InterPro: IPR005639) involved in membrane insertion and pore formation; a beta-sheet central domain involved in receptor binding; and a C-terminal beta-sandwich domain (InterPro: IPR005638) that interacts with the N-terminal domain to form a channel.[1][3]

Types edit

B. thuringiensis encodes many proteins of the delta endotoxin family (InterPro: IPR038979), with some strains encoding multiple types simultaneously.[9] A gene mostly found on plasmids,[10] delta-entotoxins sometimes show up in genomes of other species, albeit at a lower proportion than those found in B. thuringiensis.[11] The gene names looks like Cry3Bb, which in this case indicates a Cry toxin of superfamily 3 family B subfamily b.[12]

Cry proteins that are interesting to cancer research are listed under a parasporin (PS) nomenclature in addition to the Cry nomenclature. They do not kill insects, but instead kill leukemia cells.[13][14][15] The Cyt toxins tend to form their own group distinct from Cry toxins.[16] Not all Cry — crystal-form — toxins directly share a common root.[17] Examples of non-three-domain toxins that nevertheless have a Cry name include Cry34/35Ab1 and related beta-sandwich binary (Bin-like) toxins, Cry6Aa, and many beta-sandwich parasporins.[18]

Specific delta-endotoxins that have been inserted with genetic engineering include Cry3Bb1 found in MON 863 and Cry1Ab found in MON 810, both of which are maize/corn cultivars. Cry3Bb1 is particularly useful because it kills Coleopteran insects such as the corn rootworm, an activity not seen in other Cry proteins.[1] Other common toxins include Cry2Ab and Cry1F in cotton and maize/corn.[19] In addition, Cry1Ac is effective as a vaccine adjuvant in humans.[20]

Some insects populations have started to develop resistance towards delta endotoxin, with five resistant species found as of 2013. Plants with two kinds of delta endotoxins tend to make resistance happen slower, as the insects have to evolve to overcome both toxins at once. Planting non-Bt plants with the resistant plants will reduce the selection pressure for developing the toxin. Finally, two-toxin plants should not be planted with one-toxin plants, as one-toxin plants act as a stepping stone for adaption in this case.[19]

References edit

  1. ^ a b c d Galitsky N, Cody V, Wojtczak A, Ghosh D, Luft JR, Pangborn W, English L (August 2001). "Structure of the insecticidal bacterial delta-endotoxin Cry3Bb1 of Bacillus thuringiensis". Acta Crystallographica. Section D, Biological Crystallography. 57 (Pt 8): 1101–1109. doi:10.1107/S0907444901008186. PMID 11468393.
  2. ^ Roger Hull; et al. (2021). "Risk assessment and management—Environment". Genetically Modified Plants (second ed.). Upon sporulation, B. thuringiensis forms proteinaceous insecticidal δ-endotoxins either in crystals (Cry toxins) or cytoplasmically (Cyt toxins), which are encoded by cry or cyt genes, respectively. When insects ingest toxin crystals, the enzymes in their digestive tract cause the toxin to become activated. The toxin binds to the insect's gut membranes, forming a pore that results in swelling, cell lysis, and eventually killing the insect. B. thuringiensis also produces insecticidal proteins at other stages in its lifecycle, specifically the vegetative insecticidal proteins (VIPs)
  3. ^ a b Grochulski P, Masson L, Borisova S, Pusztai-Carey M, Schwartz JL, Brousseau R, Cygler M (December 1995). "Bacillus thuringiensis CryIA(a) insecticidal toxin: crystal structure and channel formation". Journal of Molecular Biology. 254 (3): 447–464. doi:10.1006/jmbi.1995.0630. PMID 7490762.
  4. ^ a b Ferré J, Van Rie J (2002). "Biochemistry and genetics of insect resistance to Bacillus thuringiensis". Annual Review of Entomology. 47 (1). Annual Reviews: 501–533. doi:10.1146/annurev.ento.47.091201.145234. PMID 11729083.
  5. ^ Soberón M, Gill SS, Bravo A (April 2009). "Signaling versus punching hole: How do Bacillus thuringiensis toxins kill insect midgut cells?". Cellular and Molecular Life Sciences. 66 (8). Springer: 1337–1349. doi:10.1007/s00018-008-8330-9. PMID 19132293. S2CID 5928827.
  6. ^ Pigott CR, Ellar DJ (June 2007). "Role of receptors in Bacillus thuringiensis crystal toxin activity". Microbiology and Molecular Biology Reviews. 71 (2). American Society for Microbiology: 255–281. doi:10.1128/mmbr.00034-06. PMC 1899880. PMID 17554045. S2CID 13982571.
  7. ^ a b c d Pardo-López L, Soberón M, Bravo A (January 2013). "Bacillus thuringiensis insecticidal three-domain Cry toxins: mode of action, insect resistance and consequences for crop protection". FEMS Microbiology Reviews. 37 (1). Federation of European Microbiological Societies (OUP): 3–22. doi:10.1111/j.1574-6976.2012.00341.x. PMID 22540421.
  8. ^ a b Vachon V, Laprade R, Schwartz JL (September 2012). "Current models of the mode of action of Bacillus thuringiensis insecticidal crystal proteins: a critical review". Journal of Invertebrate Pathology. 111 (1). Academic Press (Elsevier): 1–12. doi:10.1016/j.jip.2012.05.001. PMID 22617276.
  9. ^ "Pesticidal crystal protein (IPR038979)". InterPro. Retrieved 12 April 2019.
  10. ^ Dean DH (1984). "Biochemical genetics of the bacterial insect-control agent Bacillus thuringiensis: basic principles and prospects for genetic engineering". Biotechnology & Genetic Engineering Reviews. 2: 341–363. doi:10.1080/02648725.1984.10647804. PMID 6443645.
  11. ^ "Species: Pesticidal crystal protein (IPR038979)". InterPro.
  12. ^ "Bacillus thuringiensis Toxin Nomenclature". Bt toxin specificity database. Retrieved 12 April 2019.
  13. ^ Mizuki E, Park YS, Saitoh H, Yamashita S, Akao T, Higuchi K, Ohba M (July 2000). "Parasporin, a human leukemic cell-recognizing parasporal protein of Bacillus thuringiensis". Clinical and Diagnostic Laboratory Immunology. 7 (4): 625–634. doi:10.1128/CDLI.7.4.625-634.2000. PMC 95925. PMID 10882663.
  14. ^ Ohba M, Mizuki E, Uemori A (January 2009). "Parasporin, a new anticancer protein group from Bacillus thuringiensis". Anticancer Research. 29 (1): 427–433. PMID 19331182.
  15. ^ "List of Parasporins". Committee of Parasporin Classification and Nomenclature. Accessed Jan 4, 2013
  16. ^ Crickmore N. "Other Cry Sequences" (PDF). Retrieved 12 April 2019.
  17. ^ Crickmore N, Zeigler DR, Feitelson J, Schnepf E, Van Rie J, Lereclus D, et al. (September 1998). "Revision of the nomenclature for the Bacillus thuringiensis pesticidal crystal proteins". Microbiology and Molecular Biology Reviews. 62 (3): 807–813. doi:10.1128/MMBR.62.3.807-813.1998. PMC 98935. PMID 9729610.
  18. ^ Kelker MS, Berry C, Evans SL, Pai R, McCaskill DG, Wang NX, et al. (2014-11-12). "Structural and biophysical characterization of Bacillus thuringiensis insecticidal proteins Cry34Ab1 and Cry35Ab1". PLOS ONE. 9 (11): e112555. Bibcode:2014PLoSO...9k2555K. doi:10.1371/journal.pone.0112555. PMC 4229197. PMID 25390338.
  19. ^ a b Tabashnik BE, Brévault T, Carrière Y (June 2013). "Insect resistance to Bt crops: lessons from the first billion acres". Nature Biotechnology. 31 (6): 510–521. doi:10.1038/nbt.2597. PMID 23752438. S2CID 205278530.
  20. ^ Rodriguez-Monroy MA, Moreno-Fierros L (March 2010). "Striking activation of NALT and nasal passages lymphocytes induced by intranasal immunization with Cry1Ac protoxin". Scandinavian Journal of Immunology. 71 (3): 159–168. doi:10.1111/j.1365-3083.2009.02358.x. PMID 20415781.

Further reading edit

  • Bravo A, Gill SS, Soberón M (March 2007). "Mode of action of Bacillus thuringiensis Cry and Cyt toxins and their potential for insect control". Toxicon. 49 (4): 423–435. doi:10.1016/j.toxicon.2006.11.022. PMC 1857359. PMID 17198720.
  • Pigott CR, Ellar DJ (June 2007). "Role of receptors in Bacillus thuringiensis crystal toxin activity". Microbiology and Molecular Biology Reviews. 71 (2): 255–281. doi:10.1128/MMBR.00034-06. PMC 1899880. PMID 17554045.
  • Palma L, Muñoz D, Berry C, Murillo J, Caballero P (December 2014). "Bacillus thuringiensis toxins: an overview of their biocidal activity". Toxins. 6 (12): 3296–3325. doi:10.3390/toxins6123296. PMC 4280536. PMID 25514092.

External links edit

This article incorporates text from the public domain Pfam and InterPro: IPR015790

April 11, 2024
delta, endotoxins, endotoxins, family, pore, forming, toxins, produced, bacillus, thuringiensis, species, bacteria, they, useful, their, insecticidal, action, primary, toxin, produced, genetically, modified, maize, corn, other, crops, during, spore, formation,. Delta endotoxins d endotoxins are a family of pore forming toxins produced by Bacillus thuringiensis species of bacteria They are useful for their insecticidal action and are the primary toxin produced by the genetically modified GM Bt maize corn and other GM crops During spore formation the bacteria produce crystals of such proteins hence the name Cry toxins that are also known as parasporal bodies next to the endospores as a result some members are known as a parasporin The Cyt cytolytic toxin group is another group of delta endotoxins formed in the cytoplasm VIP toxins vegetative insecticidal proteins are formed at other stages of the life cycle 2 Delta endotoxin N terminal domaincrystal structure of the insecticidal bacterial del endotoxin Cry3Bb1 Bacillus thuringiensis 1 IdentifiersSymbolEndotoxin NPfamPF03945InterProIPR005639SCOP21dlc SCOPe SUPFAMTCDB1 C 2Available protein structures Pfam structures ECOD PDBRCSB PDB PDBe PDBjPDBsumstructure summaryDelta endotoxin middle domainIdentifiersSymbolEndotoxin MPfamPF00555Pfam clanCL0568InterProIPR015790SCOP21dlc SCOPe SUPFAMTCDB1 C 2Available protein structures Pfam structures ECOD PDBRCSB PDB PDBe PDBjPDBsumstructure summaryDelta endotoxin middle domain Cry2A and Cry18insecticidal crystal protein cry2aaIdentifiersSymbolEndotoxin midPfamPF09131InterProIPR015214SCOP21i5p SCOPe SUPFAMAvailable protein structures Pfam structures ECOD PDBRCSB PDB PDBe PDBjPDBsumstructure summaryDelta endotoxin C terminalIdentifiersSymbolEndotoxin CPfamPF03944Pfam clanCL0202InterProIPR005638SCOP21dlc SCOPe SUPFAMTCDB1 C 2CDDcd04085Available protein structures Pfam structures ECOD PDBRCSB PDB PDBe PDBjPDBsumstructure summaryCytolytic delta endotoxin Cyt1 2IdentifiersSymbolCytBPfamPF01338InterProIPR001615SCOP21cby SCOPe SUPFAMTCDB1 C 71Available protein structures Pfam structures ECOD PDBRCSB PDB PDBe PDBjPDBsumstructure summary Contents 1 Mechanism of action 2 Structure 3 Types 4 References 5 Further reading 6 External linksMechanism of action editWhen an insect ingests these proteins they are activated by proteolytic cleavage The N terminus is cleaved in all of the proteins and a C terminal extension is cleaved in some members Once activated the endotoxin binds to the gut epithelium and causes cell lysis by the formation of cation selective channels which leads to death 3 1 For many years there was no clarity as to the relationship between aminopeptidase N and Bt toxins Although AP N does bind Cry proteins in vitro 4 reviewed by Soberon et al 2009 5 and Pigott amp Ellar 2007 6 7 no cases of resistance or even reduced in vitro binding due to AP N structure alteration were known through 2002 and there was some doubt that the resistance mechanism was so straight forward Indeed Luo et al 1997 Mohammed et al 1996 and Zhu et al 2000 positively found this to not occur in Lepidoptera examples 4 Subsequently however Herrero et al 2005 showed correlation between nonexpression and Bt resistance 7 and actual resistance was found in Helicoverpa armigera by Zhang et al 2009 7 8 in Ostrinia nubilalis by Khajuria et al 2011 and in Trichoplusia ni by Baxter et al 2011 and Tiewsiri amp Wang 2011 also all Lepidoptera 7 There continues to be confirmation that AP Ns do not by themselves affect resistance in some cases possibly due to sequential binding by the toxin being required to produce its effect In this sequence each binding step is theoretically not indispensable but if it occurs does contribute to the final pore formation result 8 Structure editThe activated region of the delta toxin is composed of three distinct structural domains an N terminal helical bundle domain InterPro IPR005639 involved in membrane insertion and pore formation a beta sheet central domain involved in receptor binding and a C terminal beta sandwich domain InterPro IPR005638 that interacts with the N terminal domain to form a channel 1 3 Types editB thuringiensis encodes many proteins of the delta endotoxin family InterPro IPR038979 with some strains encoding multiple types simultaneously 9 A gene mostly found on plasmids 10 delta entotoxins sometimes show up in genomes of other species albeit at a lower proportion than those found in B thuringiensis 11 The gene names looks like Cry3Bb which in this case indicates a Cry toxin of superfamily 3 family B subfamily b 12 Cry proteins that are interesting to cancer research are listed under a parasporin PS nomenclature in addition to the Cry nomenclature They do not kill insects but instead kill leukemia cells 13 14 15 The Cyt toxins tend to form their own group distinct from Cry toxins 16 Not all Cry crystal form toxins directly share a common root 17 Examples of non three domain toxins that nevertheless have a Cry name include Cry34 35Ab1 and related beta sandwich binary Bin like toxins Cry6Aa and many beta sandwich parasporins 18 Specific delta endotoxins that have been inserted with genetic engineering include Cry3Bb1 found in MON 863 and Cry1Ab found in MON 810 both of which are maize corn cultivars Cry3Bb1 is particularly useful because it kills Coleopteran insects such as the corn rootworm an activity not seen in other Cry proteins 1 Other common toxins include Cry2Ab and Cry1F in cotton and maize corn 19 In addition Cry1Ac is effective as a vaccine adjuvant in humans 20 Some insects populations have started to develop resistance towards delta endotoxin with five resistant species found as of 2013 Plants with two kinds of delta endotoxins tend to make resistance happen slower as the insects have to evolve to overcome both toxins at once Planting non Bt plants with the resistant plants will reduce the selection pressure for developing the toxin Finally two toxin plants should not be planted with one toxin plants as one toxin plants act as a stepping stone for adaption in this case 19 References edit a b c d Galitsky N Cody V Wojtczak A Ghosh D Luft JR Pangborn W English L August 2001 Structure of the insecticidal bacterial delta endotoxin Cry3Bb1 of Bacillus thuringiensis Acta Crystallographica Section D Biological Crystallography 57 Pt 8 1101 1109 doi 10 1107 S0907444901008186 PMID 11468393 Roger Hull et al 2021 Risk assessment and management Environment Genetically Modified Plants second ed Upon sporulation B thuringiensis forms proteinaceous insecticidal d endotoxins either in crystals Cry toxins or cytoplasmically Cyt toxins which are encoded by cry or cyt genes respectively When insects ingest toxin crystals the enzymes in their digestive tract cause the toxin to become activated The toxin binds to the insect s gut membranes forming a pore that results in swelling cell lysis and eventually killing the insect B thuringiensis also produces insecticidal proteins at other stages in its lifecycle specifically the vegetative insecticidal proteins VIPs a b Grochulski P Masson L Borisova S Pusztai Carey M Schwartz JL Brousseau R Cygler M December 1995 Bacillus thuringiensis CryIA a insecticidal toxin crystal structure and channel formation Journal of Molecular Biology 254 3 447 464 doi 10 1006 jmbi 1995 0630 PMID 7490762 a b Ferre J Van Rie J 2002 Biochemistry and genetics of insect resistance to Bacillus thuringiensis Annual Review of Entomology 47 1 Annual Reviews 501 533 doi 10 1146 annurev ento 47 091201 145234 PMID 11729083 Soberon M Gill SS Bravo A April 2009 Signaling versus punching hole How do Bacillus thuringiensis toxins kill insect midgut cells Cellular and Molecular Life Sciences 66 8 Springer 1337 1349 doi 10 1007 s00018 008 8330 9 PMID 19132293 S2CID 5928827 Pigott CR Ellar DJ June 2007 Role of receptors in Bacillus thuringiensis crystal toxin activity Microbiology and Molecular Biology Reviews 71 2 American Society for Microbiology 255 281 doi 10 1128 mmbr 00034 06 PMC 1899880 PMID 17554045 S2CID 13982571 a b c d Pardo Lopez L Soberon M Bravo A January 2013 Bacillus thuringiensis insecticidal three domain Cry toxins mode of action insect resistance and consequences for crop protection FEMS Microbiology Reviews 37 1 Federation of European Microbiological Societies OUP 3 22 doi 10 1111 j 1574 6976 2012 00341 x PMID 22540421 a b Vachon V Laprade R Schwartz JL September 2012 Current models of the mode of action of Bacillus thuringiensis insecticidal crystal proteins a critical review Journal of Invertebrate Pathology 111 1 Academic Press Elsevier 1 12 doi 10 1016 j jip 2012 05 001 PMID 22617276 Pesticidal crystal protein IPR038979 InterPro Retrieved 12 April 2019 Dean DH 1984 Biochemical genetics of the bacterial insect control agent Bacillus thuringiensis basic principles and prospects for genetic engineering Biotechnology amp Genetic Engineering Reviews 2 341 363 doi 10 1080 02648725 1984 10647804 PMID 6443645 Species Pesticidal crystal protein IPR038979 InterPro Bacillus thuringiensis Toxin Nomenclature Bt toxin specificity database Retrieved 12 April 2019 Mizuki E Park YS Saitoh H Yamashita S Akao T Higuchi K Ohba M July 2000 Parasporin a human leukemic cell recognizing parasporal protein of Bacillus thuringiensis Clinical and Diagnostic Laboratory Immunology 7 4 625 634 doi 10 1128 CDLI 7 4 625 634 2000 PMC 95925 PMID 10882663 Ohba M Mizuki E Uemori A January 2009 Parasporin a new anticancer protein group from Bacillus thuringiensis Anticancer Research 29 1 427 433 PMID 19331182 List of Parasporins Committee of Parasporin Classification and Nomenclature Accessed Jan 4 2013 Crickmore N Other Cry Sequences PDF Retrieved 12 April 2019 Crickmore N Zeigler DR Feitelson J Schnepf E Van Rie J Lereclus D et al September 1998 Revision of the nomenclature for the Bacillus thuringiensis pesticidal crystal proteins Microbiology and Molecular Biology Reviews 62 3 807 813 doi 10 1128 MMBR 62 3 807 813 1998 PMC 98935 PMID 9729610 Kelker MS Berry C Evans SL Pai R McCaskill DG Wang NX et al 2014 11 12 Structural and biophysical characterization of Bacillus thuringiensis insecticidal proteins Cry34Ab1 and Cry35Ab1 PLOS ONE 9 11 e112555 Bibcode 2014PLoSO 9k2555K doi 10 1371 journal pone 0112555 PMC 4229197 PMID 25390338 a b Tabashnik BE Brevault T Carriere Y June 2013 Insect resistance to Bt crops lessons from the first billion acres Nature Biotechnology 31 6 510 521 doi 10 1038 nbt 2597 PMID 23752438 S2CID 205278530 Rodriguez Monroy MA Moreno Fierros L March 2010 Striking activation of NALT and nasal passages lymphocytes induced by intranasal immunization with Cry1Ac protoxin Scandinavian Journal of Immunology 71 3 159 168 doi 10 1111 j 1365 3083 2009 02358 x PMID 20415781 Further reading editBravo A Gill SS Soberon M March 2007 Mode of action of Bacillus thuringiensis Cry and Cyt toxins and their potential for insect control Toxicon 49 4 423 435 doi 10 1016 j toxicon 2006 11 022 PMC 1857359 PMID 17198720 Pigott CR Ellar DJ June 2007 Role of receptors in Bacillus thuringiensis crystal toxin activity Microbiology and Molecular Biology Reviews 71 2 255 281 doi 10 1128 MMBR 00034 06 PMC 1899880 PMID 17554045 Palma L Munoz D Berry C Murillo J Caballero P December 2014 Bacillus thuringiensis toxins an overview of their biocidal activity Toxins 6 12 3296 3325 doi 10 3390 toxins6123296 PMC 4280536 PMID 25514092 External links editCry3Bb1 at the United States Environmental Protection Agency This article incorporates text from the public domain Pfam and InterPro IPR015790 Retrieved from https en wikipedia org w index php title Delta endotoxins amp oldid 1215687499, wikipedia, wiki, book, books, library,

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