4gtu | pdb_00004gtu
LIGAND-FREE HOMODIMERIC HUMAN GLUTATHIONE S-TRANSFERASE M4-4
Structural highlights
Function[GSTM4_HUMAN] Conjugation of reduced glutathione to a wide number of exogenous and endogenous hydrophobic electrophiles. Active on 1-chloro-2,4-dinitrobenzene. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe 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. An asparagine-phenylalanine substitution accounts for catalytic differences between hGSTM3-3 and other human class mu glutathione S-transferases.,Patskovsky YV, Patskovska LN, Listowsky I Biochemistry. 1999 Dec 7;38(49):16187-94. PMID:10587441[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences | ||||||||||||||||||||||
