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PDBsum entry 1mtc
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Local protein dynamics and catalysis: detection of segmental motion associated with rate-Limiting product release by a glutathione transferase.
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Authors
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S.G.Codreanu,
J.E.Ladner,
G.Xiao,
N.V.Stourman,
D.L.Hachey,
G.L.Gilliland,
R.N.Armstrong.
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Ref.
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Biochemistry, 2002,
41,
15161-15172.
[DOI no: ]
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PubMed id
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Abstract
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Glutathione transferase rGSTM1-1 catalyzes the addition of glutathione (GSH) to
1-chloro-2,4-dinitrobenzene, a reaction in which the chemical step is 60-fold
faster than the physical step of product release. The hydroxyl group of Y115,
located in the active site access channel, controls the egress of product from
the active site. The Y115F mutant enzyme has a k(cat) (72 s(-)(1)) that is
3.6-fold larger than that of the native enzyme (20 s(-)(1)). Crystallographic
observations and evidence from amide proton exchange kinetics are consistent
with localized increases in the degree of segmental motion of the Y115F mutant
that are coupled to the enhanced rate of product release. The loss of hydrogen
bonding interactions involving the hydroxyl group of Y115 is reflected in subtle
alterations in the backbone position, an increase in B-factors for structural
elements that comprise the channel to the active site, and, most dramatically, a
loss of well-defined electron density near the site of mutation. The kinetics of
amide proton exchange are also enhanced by a factor between 3 and 12 in these
regions, providing direct, quantitative evidence for changes in local protein
dynamics affecting product release. The enhanced product release rate is
proposed to derive from a small shift in the equilibrium population of protein
conformers that permit egress of the product from the active site.
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