Identification and characterization of the receptor for the Bacillus sphaericus binary toxin in the malaria vector mosquito, Anopheles gambiae.
The binary toxin (Bin) from Bacillus sphaericus exhibits a highly insecticidal activity against Culex and Anopheles mosquitoes. The cytotoxicity of Bin requires an interaction with a specific receptor present on the membrane of midgut epithelial cells in larvae. A direct correlation exists between binding affinity and toxicity. The toxin binds with high affinity to its receptor in its primary target, Culex pipiens, and displays a lower affinity to the receptor in Anopheles gambiae, which is less sensitive to Bin. Although the Bin receptor has previously been identified and named Cpm1 in C. pipiens, its structure in Anopheles remains unknown. In this study, we hypothesize that the Anopheles Bin receptor is an ortholog of Cpm1. By screening the Anopheles genomic database, we identified a candidate gene (Agm3) which is expressed primarily on the surface of midgut cells in larvae and which functions as a receptor for Bin. A Cpm1-like gene is also present in the Bin-refractory species Aedes aegypti. Overall, our results indicate that the three mosquito genes examined share a very similar organization and are strongly conserved at the amino acid level, in particular in the NH(2)-terminus, a region believed to contain the ligand binding site, suggesting that relatively few amino acids residues are critical for high affinity binding of the toxin.
Opota
Onya
O
UMR1112 Réponses des Organismes aux Stress Environnementaux, INRA-UNSA, 400 Route des Chappes, BP 167, F-06903 Sophia-Antipolis, France.
Charles
Jean-François
JF
Warot
Sylvie
S
Pauron
David
D
Darboux
Isabelle
I
D000595:Amino Acid Sequence; D000818:Animals; D000852:Anopheles / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D001483:Base Sequence; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics; D004199:Disease Vectors; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D017344:Genes, Insect; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007814:Larva / Q000378:metabolism; D008288:Malaria / Q000469:parasitology*; D008969:Molecular Sequence Data; D011485:Protein Binding; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment
D001427:Bacterial Toxins; D018076:DNA, Complementary; D019476:Insect Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C046134:binB protein, Bacillus sphaericus