A single amino acid substitution converts a carboxylesterase to an organophosphorus hydrolase and confers insecticide resistance on a blowfly

• Published in: Proceedings of the National Academy of Sciences - PNAS 1997-07, Vol.94 (14), p.7464-7468
• Main Authors: Newcomb, R.D. (Horticulture and Food Research Institute of New Zealand, Ltd., Auckland, New Zealand.), Campbell, P.M, Ollis, D.L, Cheah, E, Russell, R.J, Oakeshott, J.G
• Format: Article
• Language: English
• Subjects: ACIDE ASPARTIQUE; ACIDO ASPARTICO; ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; ALLELES; Amino acids; Amino Acids - genetics; Animals; Aryldialkylphosphatase; ASPARTIC ACID; Biochemistry; Biological Sciences; CARBOXILESTERASA; CARBOXYLESTERASE; Carboxylic Ester Hydrolases - genetics; CHANGE; CLONACION; CLONAGE; CLONING; Complementary DNA; DIAZINON; Diptera - drug effects; Diptera - genetics; E3 GENE; Enzymes; ENZYMIC ACTIVITY; Esterases - genetics; GENE; GENES; Genetic mutation; Genetics; GLICINA; GLYCINE (ACIDE AMINE); GLYCINE (AMINO ACID); HIDROLASAS; HYDROLASE; HYDROLASES; Hydrolysis; INDUCED MUTATION; INSECTICIDAS; INSECTICIDE; Insecticide Resistance - genetics; INSECTICIDES; Insects; LCALPHAE7 GENE; LUCILIA CUPRINA; Molecules; MUTACION; MUTACION INDUCIDA; MUTANT; MUTANTES; MUTANTS; MUTATION; MUTATION PROVOQUEE; Pain; Pesticides; Phenotypes; Point Mutation; RESISTANCE AUX PRODUITS CHIMIQUES; RESISTANCE TO CHEMICALS; RESISTENCIA A PRODUCTOS QUIMICOS; STRUCTURAL GENES
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.94.14.7464

Resistance to organophosphorus (OP) insecticides is associated with decreased carboxylesterase activity in several insect species. It has been proposed that the resistance may be the result of a mutation in a carboxylesterase that simultaneously reduces its carboxylesterase activity and confers an OP hydrolase activity (the "mutant aliesterase hypothesis"). In the sheep blowfly, Lucilia cuprina, the association is due to a change in a specific esterase isozyme, E3, which, in resistant flies, has a null phenotype on gels stained using standard carboxylesterase substrates. Here we show that an OP-resistant allele of the gene that encodes E3 differs at five amino acid replacement sites from a previously described OP-susceptible allele. Knowledge of the structure of a related enzyme (acetylcholinesterase) suggests that one of these substitutions (Gly 137 replaced by Asp) lies within the active site of the enzyme. The occurrence of this substitution is completely correlated with resistance across 15 isogenic strains. In vitro expression of two natural and two synthetic chimeric alleles shows that the Asp 137 substitution alone is responsible for both the loss of E3's carboxylesterase activity and the acquisition of a novel OP hydrolase activity. Modeling of Asp137 in the homologous position in acetylcholinesterase suggests that Asp 137 may act as a base to orientate a water molecule in the appropriate position for hydrolysis of the phosphorylated enzyme intermediate