title: The crystal structures of glutathione S-transferases isozymes 1-3 and 1-4 from Anopheles dirus species B.
abstract: Glutathione S-transferases (GSTs) are dimeric proteins that play an important role in cellular detoxification. Four GSTs from the mosquito Anopheles dirus species B (Ad), an important malaria vector in South East Asia, are produced by alternate splicing of a single transcription product and were previously shown to have detoxifying activity towards pesticides such as DDT. We have determined the crystal structures for two of these alternatively spliced proteins, AdGST1-3 (complexed with glutathione) and AdGST1-4 (apo form), at 1.75 and 2.45 A resolution, respectively. These GST isozymes show differences from the related GST from the Australian sheep blowfly Lucilia cuprina; in particular, the presence of a C-terminal helix forming part of the active site. This helix causes the active site of the Anopheles GSTs to be enclosed. The glutathione-binding helix alpha2 and flanking residues are disordered in the AdGST1-4 (apo) structure, yet ordered in the AdGST1-3 (GSH-bound) structure, suggesting that insect GSTs operate with an induced fit mechanism similar to that found in the plant phi- and human pi-class GSTs. Despite the high overall sequence identities, the active site residues of AdGST1-4 and AdGST1-3 have different conformations.
authors.affiliation: Department of Pharmacology/Crystallography Centre, University of Western Australia, Crawley 6009, Australia.
authors.forename: A J
authors.initials: AJ
authors.lastname: Oakley
authors.forename: T
authors.initials: T
authors.lastname: Harnnoi
authors.forename: R
authors.initials: R
authors.lastname: Udomsinprasert
authors.forename: K
authors.initials: K
authors.lastname: Jirajaroenrat
authors.forename: A J
authors.initials: AJ
authors.lastname: Ketterman
authors.forename: M C
authors.initials: MC
authors.lastname: Wilce
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D000852:Anopheles / Q000201:enzymology* / Q000235:genetics; D001210:Asia, Southeastern; D001665:Binding Sites; D003461:Crystallography; D004351:Drug Resistance / Q000235:genetics; D005091:Exons; D005982:Glutathione Transferase / Q000737:chemistry* / Q000235:genetics; D007303:Insect Vectors; D007527:Isoenzymes / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment
chemical_list: D007527:Isoenzymes; D005982:Glutathione Transferase