3gtu
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(New page: 200px<br /> <applet load="3gtu" size="450" color="white" frame="true" align="right" spinBox="true" caption="3gtu, resolution 2.8Å" /> '''LIGAND-FREE HETERODI...)
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Revision as of 21:42, 12 November 2007
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LIGAND-FREE HETERODIMERIC HUMAN GLUTATHIONE S-TRANSFERASE M2-3 (EC 2.5.1.18), MONOCLINIC CRYSTAL FORM
Overview
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.
About this Structure
3GTU is a Protein complex structure of sequences from Homo sapiens. Active as Glutathione transferase, with EC number 2.5.1.18 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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