Part:BBa_K5184076
G1M5 tag-HxTx-Hv1h-GNA
Abstract
This composite part is an expression box for the basic part HxTx-Hv1h (BBa_K5184032), which allows the HxTx-Hv1h-GNA fusion protein, with high contact and oral toxicity, to achieve soluble expression in E. coli. This composite part includes a G1M5-SUMO (BBa_K5184022) compound tag is annexed to the N-terminus of the fusion protein, which facilitates the protein's correct folding and therefore its soluble expression. GNA, Galanthus nivalis agglutinin (BBa_K1974020) is attached to the C-terminus of the venom peptide, protecting it and conducting it in and through insect guts; achieving high oral and contact toxicity.
Usage and Biology
G1M5 is the mutated, less hydrophobic version of the secretion signal peptide of the G1 cyclomaltodextrin glucanotransferase (CGtase) of Bacillus sp., which allows the extracellular secretion of the bacterial enzyme. Conduction of proteins attached by G1M5 out of the cytosol is achieved by the Sec pathway, a very common secretion system seen in all three major domains of life: arachaea, prokaryote, and eukaryotes. Once the signal peptide, in this case G1M5 is synthesized, the protein chaperon SecB binds to the preprotein (that is attached to G1M5), and transfers the preprotein to the protein translocase SecA, of which binds to the membrane bound protein conducting channel SecYEG. Once bound to the membrane, SecA binds to a molecule of ATP, of which is hydrolyzed to conduct the protein through heterotrimer complex of SecYEG. A membrane bound SPaseI then, once enough of the preprotein had been conducted through the channel, will remove the SP and allow the preprotein to fold properly into the correct protein.[1] The in vivo SUMO tags, or small ubiquitin-like modifiers, are a diverse class of ubiquitin-related proteins that allow a versatile range of operations to be carried on a tagged protein. Amongst many of these is the selective proteolysis that removes the SUMO tag from the attached protein. Its ability to be detected and removed with high precision leads to the creation of the recombinant SUMO tag: a SUMO tag that, while different enough to the wildtype SUMO tag to not be degraded within eukaryotic hosts, can be detected and have the SUMO removed by special recombinant SUMO proteases. The recombinant SUMO therefore presents themselves as precise markers for points for proteolytic digestion that can remove attached (to SUMO tag) protein domains. SUMO tags also share high level of homology with the ubiquitin, and therefore, once synthesized, folds rapidly to hide its hydrophobic cores. It is proposed that this initial folding assists in the correct folding of the attached fusion protein by supplying a great initial "kinetic push". While this can explain SUMO tag's ability to facilitate protein folding and enhance soluble expression, there are also theories proposing the SUMO tag to work as a chaperone to assists in the attached protein's folding[2]
HxTx-Hv1h is a 39aa long peptide containing 6 cysteine residues arranged to create a cysteine framework of C1xxxC2xxxC3C4xxxC5xxxC6, forming cysteine cross bridges between C1C4, C2C6, and between C3C5 [Fig1A].
Paralysis and mortal effects of susceptible subjects are achieved via HxTx-Hv1h inhibition on both CaV and KCa channels of susceptible targets by blocking the channels directly, resulting in impediment of fundamental nervous system responses in neuronal, muscular, and cardiac functions. (Specific site of inhibition depends on the concentration of neurotoxin).
Galanthus nivalis agglutinin (GNA), a plant derived mannose-specific lectin that provides resistance to enzyme-meditated proteolytic activity in insect gastrointestinal tract is introduced and fused with the venom peptides. GNA is able to transport attached peptides across the insect gut, allowing delivery to the circulatory system. Thus, GNA allows enhanced oral and contact toxicity for the fusion proteins.[3]
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21COMPATIBLE WITH RFC[21]
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000COMPATIBLE WITH RFC[1000]
Toxicity Verification
HxTx-Hv1h is synthesized using the vector pET28a-G1M5-His-SUMO-HxTx-Hv1h-GNA-His[Fig2B], of which is assembled using GoldenGate cloning and transformed into E. coli strain DH5ɑ. Colony PCR and sequencing is then carried out to verify the plasmid construct, of which is extracted and transformed into BL21(DE3) strain for expression. After IPTG induction and overnight incubation, the liquid culture is harvested and, after cell lysis, have an SDS-PAGE run. The results suggest that HxTx-Hv1h had achieved soluble expression. After several unsuccessful purification attempts, the supernatant is treated directly by SUMO protease [Fig2C].
The SUMO-digested supernatant's toxicity against T. urticae females is tested using a spraying method by Professor Huang from SCAU. Results from the toxicity assay suggests HxTx-Hv1h to be highly toxic against T. urticae, achieving an fatality of 90.91% within 72 hours.
Reference
[1]Liu, Changjun, et al. ‘A Secretory System for Extracellular Production of Spider Neurotoxin Huwentoxin-I in Escherichia Coli’. Preparative Biochemistry & Biotechnology, vol. 53, no. 8, Sept. 2023, pp. 914–22. DOI.org (Crossref), https://doi.org/10.1080/10826068.2022.2158473
[2]Jürgen Dohmen, R. ‘SUMO Protein Modification’. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, vol. 1695, no. 1–3, Nov. 2004, pp. 113–31. DOI.org (Crossref), https://doi.org/10.1016/j.bbamcr.2004.09.021
[3]Sukiran, Nur Afiqah, et al. “Enhancing the Oral and Topical Insecticidal Efficacy of a Commercialized Spider Venom Peptide Biopesticide via Fusion to the Carrier Snowdrop Lectin ( Galanthus Nivalis Agglutinin).” Pest Management Science, vol. 79, no. 1, Jan. 2023, pp. 284–94. DOI.org (Crossref), https://doi.org/10.1002/ps.7198
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