Residues of Legume AG41 Peptide Crucial to Its Bio-Insecticidal Activity

Abstract

Currently, crop protection relies heavily on chemical treatments, which ultimately leads to environmental contamination and pest resistance. Societal and public policy considerations urge the need for new eco-friendly solutions. In this perspective, biopesticides are effective alternatives to chemical insecticides for the control of various insect pests. Legumes contain numerous insecticidal proteins aimed at protecting their high nitrogen content from animal/insect predation. Investigating one such protein family at genome scale, we discovered a unique diversity of the albumin 1 family in the (model) barrel medic genome. Only some members retained very high insecticidal activity. We uncovered that AG41 peptide from the alfalfa roots displays an outstanding insecticidal activity against several pests such as aphids and weevils. Here we report the 3D structure and activity of AG41 peptide. Significant insights into the structural/functional relationships explained AG41 high insecticidal activity. Such observations pave the way for the development of bio-insecticides, with AG41 peptide as the lead compound.

Diversity of Insecticidal PA1b Homologs among Legume Seeds from Middle Eastern Region

“…We followed the annotation of Pisum sativum A1 preproprotein including PA1b sequence (37 amino acids) and PA1a sequence (53 amino acids). Three disulfide bridges engage 3 cystine binding C1-C4, C2-C5, and C3-C6 at positions (3-20), (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) and (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32) respectively. Moreover, a triple-stranded antiparallel beta-sheet (residues 4 to 7, 21 to 23 and 30 to 33) along with the disulfide bonds constitute a signature of the ICK family.…”

“…The loop L2 contains the main hydrophobic residues that play a significant role in the binding and cellular toxicity of A1b peptides. The hydrophobic role in AG41 is formed by the following residues Leu27, Pro28, Trp29, Leu 31, Phe 32 and Phe 33 by facing residues Pro12 and Phe 13 of L1 26 , whereas PA1b displayed the following residues Val25, Leu27, Val28 and Ile29 with the facing residue Phe10 of L1 25 . Screening of hydrophobic residues in sequences from toxic seeds was done.…”

“…The results demonstrated that variants exhibiting a toxic effect showed different binding affinity and toxicity according to proper folding of the peptide 22 and the presence of conserved key residues specific for the recognition and the interaction of PA1b via the membrane protein-based receptor sensitive to PA1b found in various insect species and responsible for its activity 25 . This lead to the discovery of a highly toxic peptide named AG41, exhibiting ten times greater toxicity compared to PA1b and the study of its structure and biological activity 22,26 .…”

Vicia sativa subsp. sativa native to the Middle East comprises Pea Albumin1 b-like homologs: A promising natural biopesticide

“…It also has a strong cytotoxic effect against cellular Sf9 cells. The genomic DNA sequence of the PA1b homolog from this seed previously characterized [ 32 ], shows sequence identity to AG41, a PA1b homolog from the alfalfa ( Medicago truncatula ) roots displaying high insecticidal activity against weevils [ 33 ]. The resulting structural modeling of the identified sequence also shows that it has the same hydrophobic pole as AG41.…”