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4gtu

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[[Image:4gtu.gif|left|200px]]
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{{STRUCTURE_4gtu| PDB=4gtu | SCENE= }}
{{STRUCTURE_4gtu| PDB=4gtu | SCENE= }}
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'''LIGAND-FREE HOMODIMERIC HUMAN GLUTATHIONE S-TRANSFERASE M4-4'''
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===LIGAND-FREE HOMODIMERIC HUMAN GLUTATHIONE S-TRANSFERASE M4-4===
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==Overview==
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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.
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(as it appears on PubMed at http://www.pubmed.gov), where 10587441 is the PubMed ID number.
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{{ABSTRACT_PUBMED_10587441}}
==About this Structure==
==About this Structure==
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[[Category: Homodimer]]
[[Category: Homodimer]]
[[Category: Transferase]]
[[Category: Transferase]]
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Revision as of 10:40, 3 July 2008

Image:4gtu.png

Template:STRUCTURE 4gtu

LIGAND-FREE HOMODIMERIC HUMAN GLUTATHIONE S-TRANSFERASE M4-4

Template:ABSTRACT PUBMED 10587441

About this Structure

4GTU is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.

Reference

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

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