title: Bacillus thuringiensis Cry2Ab is active on Anopheles mosquitoes: single D block exchanges reveal critical residues involved in activity.
abstract: Cry2Aa exhibits dual activity to Lepidoptera and Diptera. Cry2Ab differs in amino acid sequence from Cry2Aa by 13% and has shown significant lepidopteran activity, but no mosquitocidal activity. Previous studies implicate 23 Cry2Aa specificity-conferring residues of domain II, which differ in Cry2Ab. Nine residues are putatively involved in conferring Cry2Aa dipteran specificity. To explore Cry2Ab dipteran toxicity, site-directed mutagenesis was employed to exchange Cry2Ab residues with Cry2Aa D (dipteran) block residues. Cry2Ab wild type demonstrated high toxicity (LC(50) of 540 ng mL(-1)) to Anopheles gambiae, but not to Aedes or Culex, within a 24-h time period. Cry2Ab should be reclassified as a dual active Cry toxin. Cry2Ab mutagenesis revealed critical residues for Cry2Ab protein function, as well as enhanced activity against the malarial mosquito, An. gambiae.
authors.affiliation: Department of Biochemistry, The Ohio State University, Columbus, OH 43212, USA.
authors.forename: Betina C
authors.initials: BC
authors.lastname: McNeil
authors.forename: Donald H
authors.initials: DH
authors.lastname: Dean
mesh_terms: D000330:Aedes / Q000187:drug effects; D000818:Animals; D000852:Anopheles / Q000187:drug effects*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics / Q000494:pharmacology*; D003465:Culex / Q000187:drug effects; D004731:Endotoxins / Q000235:genetics / Q000494:pharmacology*; D006460:Hemolysin Proteins / Q000235:genetics / Q000494:pharmacology*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000494:pharmacology; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D050505:Mutant Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis