2IMK

Structures of an Insect Epsilon-class Glutathione S-transferase from the Malaria Vector Anopheles Gambiae: Evidence for High DDT-detoxifying Activity

Summary for 2IMK

• Entry DOI: 10.2210/pdb2imk/pdb
• Related: 2IL3 2IMI
• Descriptor: Epsilon-class Glutathione S-transferase, S-HEXYLGLUTATHIONE (3 entities in total)
• Functional Keywords: epsilon-class glutathione; s-transferase, transferase
• Biological source: Anopheles gambiae (African malaria mosquito)
• Total number of polymer chains: 2
• Total formula weight: 50544.21

Authors

Wang, Y.,Hemingway, J.,Ranson, H.,Meehan, E.J.,Chen, L. (deposition date: 2006-10-02, release date: 2007-10-09, Last modification date: 2023-08-30)

Primary citation

Wang, Y.,Qiu, L.,Ranson, H.,Lumjuan, N.,Hemingway, J.,Setzer, W.N.,Meehan, E.J.,Chen, L.
Structure of an insect epsilon class glutathione S-transferase from the malaria vector Anopheles gambiae provides an explanation for the high DDT-detoxifying activity
J.Struct.Biol., 164:228-235, 2008

PubMed Abstract: Glutathione S-transferases (GSTs), a major family of detoxifying enzymes, play a pivotal role in insecticide resistance in insects. In the malaria vector Anopheles gambiae, insect-specific epsilon class GSTs are associated with resistance to the organochlorine insecticide DDT [1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane]. Five of the eight class members have elevated expression levels in a DDT resistant strain. agGSTe2 is considered the most important GST in conferring DDT resistance in A. gambiae, and is the only member of the epsilon class with confirmed DDT-metabolizing activity. A delta class GST from the same species shows marginal DDT-metabolizing activity but the activity of agGSTe2 is approximately 350x higher than the delta class agGST1-6. To investigate its catalytic mechanism and the molecular basis of its unusually high DDT-metabolizing ability, three agGSTe2 crystal structures including one apo form and two binary complex forms with the co-factor glutathione (GSH) or the inhibitor S-hexylglutathione (GTX) have been solved with a resolution up to 1.4A. The structure of agGSTe2 shows the canonical GST fold with a highly conserved N-domain and a less conserved C-domain. The binding of GSH or GTX does not induce significant conformational changes in the protein. The modeling of DDT into the putative DDT-binding pocket suggests that DDT is likely to be converted to DDE [1,1-dichloro-2,2-bis-(p-chlorophenyl)ethylene] through an elimination reaction triggered by the nucleophilic attack of the thiolate group of GS(-) on the beta-hydrogen of DDT. The comparison with the less active agGST1-6 provides the structural evidence for its high DDT-detoxifying activity. In short, this is achieved through the inclination of the upper part of H4 helix (H4'' helix), which brings residues Arg112, Glu116, and Phe120 closer to the GSH-binding site resulting in a more efficient GS(-)-stabilizing hydrogen-bond-network and higher DDT-binding affinity.

PubMed: 18778777
DOI: 10.1016/j.jsb.2008.08.003

Experimental method

X-RAY DIFFRACTION (1.9 Å)