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Altered GPI modification of insect AChE improves tolerance to organophosphate insecticides.
MedLine Citation:
PMID:  21112395     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The olive fruit fly Bactrocera oleae is the most destructive and intractable pest of olives. The management of B. oleae has been based on the use of organophosphate (OP) insecticides, a practice that induced resistance. OP-resistance in the olive fly was previously shown to be associated with two mutations in the acetylcholinesterase (AChE) enzyme that, apparently, hinder the entrance of the OP into the active site. The search for additional mutations in the ace gene that encodes AChE revealed a short deletion of three glutamines (Δ3Q) from a stretch of five glutamines, in the C-terminal peptide that is normally cleaved and substituted by a GPI anchor. We verified that AChEs from B. oleae and other Dipterans are actually GPI-anchored, although this is not predicted by the "big-PI" algorithm. The Δ3Q mutation shortens the unusually long hydrophilic spacer that follows the predicted GPI attachment site and may thus improve the efficiency of GPI anchor addition. We expressed the wild type B. oleae AChE, the natural mutant Δ3Q and a constructed mutant lacking all 5 consecutive glutamines (Δ5Q) in COS cells and compared their kinetic properties. All constructs presented identical K(m) and k(cat) values, in agreement with the fact that the mutations did not affect the catalytic domain of the enzyme. In contrast, the mutants produced higher AChE activity, suggesting that a higher proportion of the precursor protein becomes GPI-anchored. An increase in the number of GPI-anchored molecules in the synaptic cleft may reduce the sensitivity to insecticides.
Authors:
Evdoxia G Kakani; Suzanne Bon; Jean Massoulié; Kostas D Mathiopoulos
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2010-11-26
Journal Detail:
Title:  Insect biochemistry and molecular biology     Volume:  -     ISSN:  1879-0240     ISO Abbreviation:  -     Publication Date:  2010 Nov 
Date Detail:
Created Date:  2010-12-27     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9207282     Medline TA:  Insect Biochem Mol Biol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2010 Elsevier Ltd. All rights reserved.
Affiliation:
Department of Biochemistry and Biotechnology, University of Thessaly, Ploutonos 26, Larissa 41221, Greece.
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