Identification of the receptor for Bacillus sphaericus crystal toxin in the brush border membrane of the mosquito Culex pipiens (Diptera : Culicidae)

The binary toxin (Bin) from Bacillus sphaericus crystals specifically binds to soluble midgut brush border membrane proteins from Culex pipiens larvae . A single 60 kDa midgut membrane protein is identified as the binding prot ein. This protein is anchored in the mosquito midgut membrane via a glycosy l-phosphatidylinositol (GPI) anchor, and is partially released by phosphati dylinositol specific-phospholipase C (PI-PLC). Fractionation of soluble pro teins by anion exchange chromatography indicates that the binding protein d oes not co-elute with leucine aminopeptidase activity. After partial purifi cation, the sequences of internal amino acid fragments of the 60 kDa protei n were determined. The peptide sequences were compared with data in GenBank , and showed a very high degree of similarity with enzymes belonging to the oc-amylase family. Further enzymatic investigation showed that the recepto r of the Bin toxin in C. pipiens larval midgut may be an a-glucosidase. (C) 1999 Elsevier Science Ltd. All rights reserved.