The Crystal Structure of Bacillus thuringiensis Tpp80Aa1 and Its Interaction with Galactose-Containing Glycolipids

Tpp80Aa1 from Bacillus thuringiensis is a Toxin_10 family protein (Tpp) with reported action against Culex mosquitoes. Here, we demonstrate an expanded target range, showing Tpp80Aa1 is also active against the larvae of Anopheles gambiae and Aedes aegypti mosquitoes. We report the first crystal structure of Tpp80Aa1 at a resolution of 1.8 angstrom, which shows Tpp80Aa1 consists of two domains: an N-terminal beta-trefoil domain resembling a ricin B lectin and a C-terminal putative pore-forming domain sharing structural similarity with the aerolysin family. Similar to other Tpp family members, we observe Tpp80Aa1 binds to the mosquito midgut, specifically the posterior midgut and the gastric caecum. We also identify that Tpp80Aa1 can interact with galactose-containing glycolipids and galactose, and this interaction is critical for exerting full insecticidal action against mosquito target cell lines.

Automated summary

Tpp80Aa1 from Bacillus thuringiensis is a toxin protein that shows activity against Culex mosquitoes, as well as larvae of Anopheles gambiae and Aedes aegypti mosquitoes. The crystal structure of Tpp80Aa1 reveals its two domains, resembling ricin B lectin and aerolysin family, and its binding to the midgut of mosquitoes. The interaction with galactose-containing glycolipids and galactose is crucial for its insecticidal action.