Analyses of Bacillus thuringiensis Cry11Ba receptors in mosquito Anopheles gambiae

Cry11Ba produced by Bacillus thuringiensis subsp. jegethesan is the single, most effective toxin against mosquitoes. Towards characterizing the mode of Cry11Ba action in Anopheles gambiae, we identified binding proteins in larval midgut and investigated their receptor roles. Previously, we identified an aminopeptidase (AgAPN2) and an alkaline phosphatase (AgALP1) as receptors for Cry11Ba toxin in An. gambiae. However a cadherin (AgCad1) identified as a receptor for Cry4Ba, bound Cry11Ba with low affinity (Kd=800 nM) and data do not support a Cry11Ba receptor role for AgCad1. A second cadherin, AgCad2 with only 18% identity to AgCad1, was identified in larval midgut. An E. coli expressed fragment of AgCad2 binds Cry11Ba with high affinity ( Kd=12 nm), blocks Cry11Ba binding to An. gambiae brush border vesicles and reduces Cry11Ba toxicity in bioassays. Interactions between Cry11Ba and AgAPN2, AgALP1 and AgCad2 have been characterized and the respective roles in Cry11Ba toxicity will be presented.