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Jin J, Agwa AJ, Szanto TG, Csóti A, Panyi G, Schroeder CI, Walker AA, King GF. Weaponisation 'on the fly': Convergent recruitment of knottin and defensin peptide scaffolds into the venom of predatory assassin flies. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2020; 118:103310. [PMID: 31870846 DOI: 10.1016/j.ibmb.2019.103310] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 12/12/2019] [Accepted: 12/16/2019] [Indexed: 06/10/2023]
Abstract
Many arthropod venom peptides have potential as bioinsecticides, drug leads, and pharmacological tools due to their specific neuromodulatory functions. Assassin flies (Asilidae) are a family of predaceous dipterans that produce a unique and complex peptide-rich venom for killing insect prey and deterring predators. However, very little is known about the structure and function of their venom peptides. We therefore used an E. coli periplasmic expression system to express four disulfide-rich peptides that we previously reported to exist in venom of the giant assassin fly Dolopus genitalis. After purification, each recombinant peptide eluted from a C18 column at a position closely matching its natural counterpart, strongly suggesting adoption of the native tertiary fold. Injection of purified recombinant peptides into blowflies (Lucilia cuprina) and crickets (Acheta domestica) revealed that two of the four recombinant peptides, named rDg3b and rDg12, inhibited escape behaviour in a manner that was rapid in onset (<1 min) and reversible. Homonuclear NMR solution structures revealed that rDg3b and rDg12 adopt cystine-stabilised α/ß defensin and inhibitor cystine knot folds, respectively. Although the closest known homologues of rDg3b at the level of primary structure are dipteran antimicrobial peptides such as sapecin and lucifensin, a DALI search showed that the tertiary structure of rDg3b most closely resembles the KV11.1-specific α-potassium channel toxin CnErg1 from venom of the scorpion Centruroides noxius. This is mainly due to the deletion of a large, unstructured loop between the first and second cysteine residues present in Dg3b homologues from non-asiloid, but not existing in asiloid, species. Patch-clamp electrophysiology experiments revealed that rDg3b shifts the voltage-dependence of KV11.1 channel activation to more depolarised potentials, but has no effect on KV1.3, KV2.1, KV10.1, KCa1.1, or the Drosophila Shaker channel. Although rDg12 shares the inhibitor cystine knot structure of many gating modifier toxins, rDg12 did not affect any of these KV channel subtypes. Our results demonstrate that multiple disulfide-rich peptide scaffolds have been convergently recruited into asilid and other animal venoms, and they provide insight into the molecular evolution accompanying their weaponisation.
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Affiliation(s)
- Jiayi Jin
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Akello J Agwa
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Tibor G Szanto
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, H-4032, Hungary
| | - Agota Csóti
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, H-4032, Hungary
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, H-4032, Hungary
| | - Christina I Schroeder
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Andrew A Walker
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, 4072, Australia.
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, 4072, Australia.
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Yao T, Lu J, Ye L, Wang J. Molecular characterization and immune analysis of a defensin from small abalone, Haliotis diversicolor. Comp Biochem Physiol B Biochem Mol Biol 2019; 235:1-7. [PMID: 31078702 DOI: 10.1016/j.cbpb.2019.05.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 04/18/2019] [Accepted: 05/06/2019] [Indexed: 01/09/2023]
Abstract
As one of antimicrobial peptides (AMPs), defensins are involved in invertebrate innate immunity against invading pathogens. In this study, a member of the invertebrate defensins was cloned and characterized from the small abalone Haliotis diversicolor, designated HdDef-2. The HdDef-2 cDNA contained a 201 bp open reading frame encoding 66 amino acids including a signal peptide of 18 amino acids and a mature peptide of 48 amino acids. The mature peptide of HdDef-2 possessed similar features to other AMPs, such as lower molecular mass, net positive charge (+1), and a high hydrophobic residue ratio (45%). In addition, six cysteines in the mature peptide were arranged in the pattern C-X16-C-X3-C-X9-C-X4-C-X1-C and stabilized the α-helix/β-sheet motif (CSαβ) with three disulfide bonds (C1-C4, C2-C5 and C3-C6) in the predicted tertiary structure. Moreover, the similar three-dimensional structure to Anopheles gambiae defensin and a phylogenetic analysis suggest that HdDef-2 may be a new member of the arthropod defensin family. Quantitative real-time PCR analysis revealed that HdDef-2 transcripts were constitutively expressed in the mantle, gill, hepatopancreas, and foot, with the highest level in the hepatopancreas. It was observed that HdDef-2 transcripts were significantly induced in the hepatopancreas after infection by Vibrio harveyi. These results indicate that HdDef-2 may be involved in the immune response against invading pathogenic bacteria, but future work is needed to verify its antimicrobial activity in protein level and elucidate the underlying mechanisms.
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Affiliation(s)
- Tuo Yao
- Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou Guangdong 510300, PR China
| | - Jie Lu
- Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou Guangdong 510300, PR China
| | - Lingtong Ye
- Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou Guangdong 510300, PR China
| | - Jiangyong Wang
- Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou Guangdong 510300, PR China.
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