Summary
PDB 3GTU deposited: 1998-07-29 modified: 2009-02-24
Title LIGAND-FREE HETERODIMERIC HUMAN GLUTATHIONE S-TRANSFERASE M2-3 (EC 2.5.1.18), MONOCLINIC CRYSTAL FORM
Authors Listowsky, I., Patskovska, L.N., Patskovsky, Y.V.
Method X-RAY DIFFRACTION
Structure factors resolution 2.8 rfactor 0.225 rfree 0.27
DPI 1.09 theoretical min: 0.50
Related PDB Entries 4GTU
Citations

The hGSTM3 subunit, which is preferentially expressed in germ-line cells, has the greatest sequence divergence among the human mu class glutathione S-transferases. To determine a structural basis for the catalytic differences between hGSTM3-3 and other mu class enzymes, chimeric proteins were designed by modular interchange of the divergent C-terminal domains of hGSTM3 and hGSTM5 subunits. Replacement of 24 residues of the C-terminal segment of either subunit produced chimeric enzymes with catalytic properties that reflected those of the wild-type enzyme from which the C-terminus had been derived. Deletion of the tripeptide C-terminal extension found only in the hGSTM3 subunit had no effect on catalysis. The crystal structure determined for a ligand-free hGSTM3 subunit indicates that an Asn212 residue of the C-terminal domain is near a hydrophobic cluster of side chains formed in part by Ile13, Leu16, Leu114, Ile115, Tyr119, Ile211, and Trp218. Accordingly, a series of point mutations were introduced into the hGSTM3 subunit, and it was indeed determined that a Y119F mutation considerably enhanced the turnover rate of the enzyme for nucleophilic aromatic substitution reactions. A more striking effect was observed for a double mutant (Y119F/N212F) which had a k(cat)/K(m)(CDNB) value of 7.6 x 10(5) s(-)(1) M(-)(1) as compared to 4.9 x 10(3) s(-)(1) M(-)(1) for the wild-type hGSTM3-3 enzyme. The presence of a polar Asn212 in place of a Phe residue found in the cognate position of other mu class glutathione S-transferases, therefore, has a marked influence on catalysis by hGSTM3-3.

Biochemistry 1999 Dec; 38(49):16187-16194 doi:10.1021/bi991714t

Cross References
Database source Identifier Description
PubMed 10587441 BICHAW
Biomolecule Structure Assembly Serial Assembly Type Conformational State Chains Ligands Atoms
3GTU/1 3GTU 1 dimer 0 2 0 3227
3GTU/2 3GTU 2 dimer 0 2 0 3245
3GTU/3 3GTU 3 tetramer 0 4 0 6472