Insights into the structural changes that trigger receptor binding upon proteolytic activation of Bacillus thuringiensis Vip3Aa insecticidal protein

作者：Óscar Infante, Isabel Gómez, Ángel Enrique Peláez-Aguilar, Luis A. Verduzco-Rosas, Rosalina García-Suárez, Blanca I. García‐Gómez, Zeyu Wang, Jie Zhang, Adán Guerrero, Alejandra Bravo, Mário Soberón · 发表于：PLoS Pathogens · 年份：2024 · DOI：10.1371/journal.ppat.1012765 · 被引用次数：14 · 研究领域：Insect Resistance and Genetics、Insect and Pesticide Research、Bacillus and Francisella bacterial research

Bacillus thuringiensis (Bt) bacteria produce different pore forming toxins with insecticidal activity, including Cry and Vip3 proteins. While both Cry and Vip3 cause insect death by forming pores in susceptible lepidopteran larval midgut cells, their mechanisms of action differ. The Vip3Aa protoxin adopts a tetramer-structure, where each monomer has five distinct domains. Upon proteolytic activation, the Vip3 tetramer undergoes a large conformational change forming a syringe like structure that is ready for membrane insertion and pore formation. Here we show that Vip3Aa protoxin had low binding to Spodoptera frugiperda brush border membrane vesicles (BBMV) unlike the activated toxin that bound specifically in a concentration dependent way, suggesting that a structural change upon Vip3Aa proteolytic activation is required for efficient receptor binding. Consistently, the Vip3Aa protoxin showed no toxicity to Sf9 cells compared to the activated toxin. In contrast, Cry1Fa protoxin and its activated toxin, were both highly toxic to Sf9 cells. To identify the region of Vip3 involved in binding to BBMV proteins, different overlapping peptides from Vip3Aa covering domains III, IV and V were expressed, and binding analysis were performed against BBMV, showing that domain III is the primary binding domain. Additionally, domains III, IV and V amino acid residues that become exposed upon activation of Vip3Aa were identified. Mutagenesis of these exposed residues revealed three amino aci...