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1qt4

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[[Image:1qt4.jpg|left|200px]]
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{{STRUCTURE_1qt4| PDB=1qt4 | SCENE= }}
{{STRUCTURE_1qt4| PDB=1qt4 | SCENE= }}
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'''T26Q MUTANT OF T4 LYSOZYME'''
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===T26Q MUTANT OF T4 LYSOZYME===
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==Overview==
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In contrast to hen egg-white lysozyme, which retains the beta-configuration of the substrate in the product, T4 lysozyme (T4L) is an inverting glycosidase. The substitution Thr-26 --&gt; His, however, converts T4L from an inverting to a retaining enzyme. It is shown here that the Thr-26 --&gt; His mutant is also a transglycosidase. Indeed, the transglycosylation reaction can be more effective than hydrolysis. In contrast, wild-type T4L has no detectable transglycosidase activity. The results support the prior hypothesis that catalysis by the Thr-26 --&gt; His mutant proceeds via a covalent intermediate. Further mutations (Glu-11 --&gt; His, Asp-20 --&gt; Cys) of the T26H mutant lysozyme indicate that the catalytic mechanism of this mutant requires Glu-11 as a general acid but Asp-20 is not essential. The results help provide an overall rationalization for the activity of glycosidases, in which a highly conserved acid group (Glu-11 in T4L, Glu-35 in hen egg-white lysozyme) on the beta-side of the substrate acts as a proton donor, whereas alterations in the placement and chemical identity of residues on the alpha-side of the substrate can lead to catalysis with or without retention of the configuration, to transglycosidase activity, or to the formation of a stable enzyme-substrate adduct.
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(as it appears on PubMed at http://www.pubmed.gov), where 10430876 is the PubMed ID number.
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{{ABSTRACT_PUBMED_10430876}}
==About this Structure==
==About this Structure==
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[[Category: Weaver, L H.]]
[[Category: Weaver, L H.]]
[[Category: Hydrolase]]
[[Category: Hydrolase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 06:40:38 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 14:18:57 2008''

Revision as of 11:19, 29 July 2008

Image:1qt4.png

Template:STRUCTURE 1qt4

T26Q MUTANT OF T4 LYSOZYME

Template:ABSTRACT PUBMED 10430876

About this Structure

1QT4 is a Single protein structure of sequence from Enterobacteria phage t4. Full crystallographic information is available from OCA.

Reference

Structural basis of the conversion of T4 lysozyme into a transglycosidase by reengineering the active site., Kuroki R, Weaver LH, Matthews BW, Proc Natl Acad Sci U S A. 1999 Aug 3;96(16):8949-54. PMID:10430876

Page seeded by OCA on Tue Jul 29 14:18:57 2008

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