title: Structural basis for catalytic activity of a silkworm Delta-class glutathione transferase.
abstract: BACKGROUND
  Glutathione transferase (GST) catalyzes glutathione conjugation, a major detoxification pathway for xenobiotics and endogenous substances. Here, we determined the crystal structure of a Delta-class GST from Bombyx mori (bmGSTD) to examine its catalytic residues.
  
  
  METHODS
  The three-dimensional structure of bmGSTD was resolved by the molecular replacement method and refined to a resolution of 2.0Å.
  
  
  RESULTS
  Structural alignment with a Delta-class GST of Anopheles gambiae indicated that bmGSTD contains 2 distinct domains (an N-terminal domain and a C-terminal domain) connected by a linker. The bound glutathione localized at the N-terminal domain. Putative catalytic residues were changed to alanine by site-directed mutagenesis, and the resulting mutants were characterized in terms of catalytic activity using glutathione and 1-chloro-2,4-dinitrobenzene, a synthetic substrate of GST. Kinetic analysis of bmGSTD mutants indicated that Ser11, Gln51, His52, Ser67, and Arg68 are important for enzyme function.
  
  
  CONCLUSIONS
  These results provide structural insights into the catalysis of glutathione conjugation in B. mori by bmGSTD.
authors.affiliation: Faculty of Agriculture, Kyushu University Graduate School, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. yamamok@agr.kyushu-u.ac.jp
authors.forename: Kohji
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Usuda
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Kakuta
authors.forename: Makoto
authors.initials: M
authors.lastname: Kimura
authors.forename: Akifumi
authors.initials: A
authors.lastname: Higashiura
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nakagawa
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Aso
authors.forename: Mamoru
authors.initials: M
authors.lastname: Suzuki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D012831:Bombyx / Q000201:enzymology* / Q000235:genetics; D002384:Catalysis; D020134:Catalytic Domain / Q000235:genetics; D003460:Crystallization; D004789:Enzyme Activation; D004795:Enzyme Stability / Q000235:genetics; D005982:Glutathione Transferase / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
chemical_list: D005982:Glutathione Transferase