Location of a potential transport binding site in a sigma class glutathione transferase by x-ray crystallography.
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.
Ji
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Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, Rockville, USA.
von Rosenvinge
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Johnson
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Armstrong
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Gilliland
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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
D046911:Macromolecular Substances; D011994:Recombinant Proteins; D005982:Glutathione Transferase