Identification and cloning of a key insecticide-metabolizing glutathione S-transferase (MdGST-6A) from a hyper insecticideresistant strain of the housefly Musca domestica

S. H. Wei, A. G. Clark, Michael Syvanen

Research output: Contribution to journalArticle

97 Scopus citations

Abstract

Strains of the housefly, Musca domestica, highly resistant to organophosphate (OP) and other insecticides are known because they overproduce glutathione S-transferases (GSTs). Previous work has shown that overproduction in these strains involved numerous isozymes with glutathione conjugating activities (Pesticide Biochem. Physiol., 25 (1986) 169; Mol. General Genetics, 227 (1991) 355; J. Biol. Chem., 267 (1992) 1840; Mol. General Genetics, 245 (1994) 236; J. Mol. Evol., 43 (1996) 236). The current work describes the purification and identification of a M. domestica GST isozyme (pI 7.1) broadly specific for substrates from a housefly strain, Cornell-HR, that is highly resistant against OP-insecticides, and the isolation of two new MdGST genes using the antibody made against it. This isozyme, which was identified from amongst more than 20 isoelectric forms of GSTs of the same subunit size, was highly active for conjugating GSH to the model substrate 3,4-dichloronitrobenzne (DCNB). When expressed in Escherichia coli, one of the cloned GSTs, MdGST-6A, produces an enzyme that conjugates glutathione to the insecticides methyl parathion and lindane. On indication that it was the most active isozyme toward several xenobiotics among several MdGSTs tested, we advance the notion that MdGST-6A probably plays an important role in M. domestica Cornell-HR's resistance towards OP-insecticides. MdGST-6A and a second closely related one found in this work, MdGST-6B, are members of the traditional insect class I family (theta-class) and share the greatest homologies with a cluster of Drosophila GSTs on locus 55. In addition to having the unusually broad substrate specificity, the sequence of the new group of enzymes reveals that it has a highly diverged hydrophobic motif in its active site as compared to other class I GSTs from insects.

Original languageEnglish (US)
Pages (from-to)1145-1153
Number of pages9
JournalInsect Biochemistry and Molecular Biology
Volume31
Issue number12
DOIs
StatePublished - Nov 1 2001

Keywords

  • E. coli expression
  • Glutathione S-transferase
  • GST
  • Housefly
  • Insecticide metabolism
  • Insecticide resistance
  • Molecular cloning
  • Musca domestica

ASJC Scopus subject areas

  • Insect Science
  • Biochemistry

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