Oral Presentation: 20 minutes 11th Asia-Pacific Congress of the International Society on Toxinology 2021

Isolation and characterisation of a mosquitocidal peptide from Hysterocrates gigas tarantula venom (#16)

Jamila Ahmed 1 , Volker Herzig 2 3 , Andrew Walker 4 , Hugo Perdomo 5 , Shaodong Guo 4 , Samantha Nixon 4 , Sassan Asgari 5 , Hilary I. Okoh 6 , Dalhatu M. Shehu 1 , Mohammed N. Shuaibu 7 , Iliya S. Ndams 1 , Glenn F. King 4
  1. Department of Zoology, Ahmadu Bello University, Zaria, Kaduna, Nigeria
  2. GeneCology Research Centre, University of the Sunshine Coast, Sippy Downs, Queensland, Australia
  3. School of Science, technology and engineering, University of Sunshine Coast, Sunshine Coast, Queensland, Australia
  4. Institute for molecular bioscience, The University of Queensland, Brisbane, Queensland, Australia
  5. School of Biological Science, The University of Queensland, Brisbane, Queensland, Australia
  6. Department of animal and environmental biology , Federal University Oye-Ekiti, Oye-Ekiti, Ekiti, Nigeria
  7. Department of Biochemistry, Ahmadu Bello University, Zaria, Kaduna, Nigeria

Aedes aegypti mosquitoes are important vectors of arboviruses such as chikungunya, dengue, yellow fever and Zika viruses [1], accounting for over 29,000 annual deaths with up to one third of the worlds’ population at risk, particularly in Africa, the Americas, Asia and the Pacific [2]. Effective and rapid control of these diseases relies on vector control, which is mainly achieved using chemical insecticides [3]. However, A. aegypti have been reported to be resistant to many existing chemical insecticides [4]. Thus, our study aimed at isolating mosquitocidal toxins by screening venoms sourced from 41 spider and 9 scorpion species. These screens revealed potent mosquitocidal activity in the venom of the Cameroon baboon tarantula Hysterocrates gigas. Using a combination of reversed phase and hydrophilic interaction liquid chromatography, we isolated a 40-residue peptide with an oxidized monoisotopic mass of 4502.11 Da which was named U1-TRTX-Hg1a (Hg1a) [5]. When injected into A. aegypti mosquito, the isolated Hg1a showed a LD50 of 23.2 pmol/g. In silico modelling using SwissModel predicts that the 3-dimensional structure of Hg1a conforms to the disulfide directed β-hairpin (DDH) motif having three parallel β-strands, which are stabilized by three disulfide bonds. A BLAST search using NCBI and Arachnoserver [6,7] revealed 65-72.5% sequence similarities between Hg1a and several insecticidal toxins from other tarantula species, with ⍵-TRTX-Asp1a [8] exhibiting the highest similarity. Phylogenetic analysis of Hg1a with these similar toxins using MEGA X revealed that Hg1a is closely related to U1-TRTX-Hs1a, a toxin isolated from the Chinese tarantula Cyriopagopus schmidti [9] sharing 68.3% sequence similarity. Hg1a is the first insecticidal toxin isolated from H. gigas venom with the potential to be used as a lead for controlling A. aegypti mosquitoes.

 

Key words: Hysterocrates gigas tarantula, insecticidal toxin, Aedes aegypti mosquito, disulfide directed β-hairpin

 

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