1qt8: Difference between revisions

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[[Image:1qt8.jpg|left|200px]]
{{Seed}}
[[Image:1qt8.png|left|200px]]


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{{STRUCTURE_1qt8|  PDB=1qt8  |  SCENE=  }}  
{{STRUCTURE_1qt8|  PDB=1qt8  |  SCENE=  }}  


'''T26H Mutant of T4 Lysozyme'''
===T26H Mutant of T4 Lysozyme===




==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.
The line below this paragraph, {{ABSTRACT_PUBMED_10430876}}, adds the Publication Abstract to the page
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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]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May  3 06:40:46 2008''
 
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 07:34:28 2008''

Revision as of 04:34, 28 July 2008

File:1qt8.png

Template:STRUCTURE 1qt8

T26H Mutant of T4 Lysozyme

Template:ABSTRACT PUBMED 10430876

About this Structure

1QT8 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

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