1TDI

Crystal Structure of hGSTA3-3 in Complex with Glutathione

Summary for 1TDI

• Entry DOI: 10.2210/pdb1tdi/pdb
• Related: 1gse 1guh
• Descriptor: Glutathione S-transferase A3-3, GLUTATHIONE (3 entities in total)
• Functional Keywords: gst, hgsta3-3, steroid isomerase, transferase
• Biological source: Homo sapiens (human)
• Cellular location: Cytoplasm: Q16772
• Total number of polymer chains: 2
• Total formula weight: 51292.00

Authors

Gu, Y.,Guo, J.,Pal, A.,Pan, S.S.,Zimniak, P.,Singh, S.V.,Ji, X. (deposition date: 2004-05-22, release date: 2005-01-18, Last modification date: 2023-08-30)

Primary citation

Gu, Y.,Guo, J.,Pal, A.,Pan, S.S.,Zimniak, P.,Singh, S.V.,Ji, X.
Crystal structure of human glutathione S-transferase A3-3 and mechanistic implications for its high steroid isomerase activity.
Biochemistry, 43:15673-15679, 2004

PubMed Abstract: The crystal structure of human class alpha glutathione (GSH) S-transferase A3-3 (hGSTA3-3) in complex with GSH was determined at 2.4 A. Despite considerable amino acid sequence identity with other human class alpha GSTs (e.g., hGSTA1-1), hGSTA3-3 is unique due to its exceptionally high steroid double bond isomerase activity for the transformation of Delta(5)-androstene-3,17-dione (Delta(5)-AD) to Delta(4)-androstene-3,17-dione. A comparative analysis of the active centers of hGSTA1-1 and hGSTA3-3 reveals that residues in positions 12 and 208 may contribute to their disparate isomerase activity toward Delta(5)-AD. Substitution of these two residues of hGSTA3-3 with the corresponding residues in hGSTA1-1 followed by kinetic characterization of the wild-type and the mutant enzymes supported this prediction. On the basis of our model of the hGSTA3-3.GSH.Delta(5)-AD ternary complex and available biochemical data, we propose that the thiolate group of deprotonated GSH (GS(-)) serves as a base to initiate the reaction by accepting a proton from the steroid and the nonionized hydroxyl group of catalytic residue Y9 (HO-Y9) functions as part of a proton-conducting wire to transfer a proton back to the steroid. Residue R15 may function to stabilize the deprotonated thiolate group of GSH (GS(-)), and a GSH-bound water molecule may donate a hydrogen bond to the 3-keto group of Delta(5)-AD and thus help the thiolate of GS(-) to initiate the proton transfer and the subsequent stabilization of the reaction intermediate.

PubMed: 15595823
DOI: 10.1021/bi048757g

Experimental method

X-RAY DIFFRACTION (2.4 Å)