title: Location of a potential transport binding site in a sigma class glutathione transferase by x-ray crystallography.
abstract: The crystal structure of the sigma class glutathione transferase from squid digestive gland in complex with S-(3-iodobenzyl)glutathione reveals a third binding site for the glutathione conjugate besides the two in the active sites of the dimer. The additional binding site is near the crystallographic two-fold axis between the two alpha 4-turn-alpha 5 motifs. The principal binding interactions with the conjugate include specific electrostatic interactions between the peptide and the two subunits and a hydrophobic cavity found across the two-fold axis that accommodates the 3-iodobenzyl group. Thus, two identical, symmetry-related but mutually exclusive binding modes for the third conjugate are observed. The hydrophobic pocket is about 14 A from the hydroxyl group of Tyr-7 in the active site. This site is a potential transport binding site for hydrophobic molecules or their glutathione conjugates.
authors.affiliation: Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, Rockville, USA.
authors.forename: X
authors.initials: X
authors.lastname: Ji
authors.forename: E C
authors.initials: EC
authors.lastname: von Rosenvinge
authors.forename: W W
authors.initials: WW
authors.lastname: Johnson
authors.forename: R N
authors.initials: RN
authors.lastname: Armstrong
authors.forename: G L
authors.initials: GL
authors.lastname: Gilliland
mesh_terms: D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D049832:Decapodiformes / Q000201:enzymology; D005982:Glutathione Transferase / Q000737:chemistry* / Q000648:ultrastructure; D019077:Helix-Turn-Helix Motifs; D046911:Macromolecular Substances; D008958:Models, Molecular; D011994:Recombinant Proteins
chemical_list: D046911:Macromolecular Substances; D011994:Recombinant Proteins; D005982:Glutathione Transferase