1qt3: Difference between revisions
New page: left|200px<br /><applet load="1qt3" size="450" color="white" frame="true" align="right" spinBox="true" caption="1qt3, resolution 1.85Å" /> '''T26D MUTANT OF T4 LY... |
No edit summary |
||
| Line 1: | Line 1: | ||
[[Image:1qt3.jpg|left|200px]]<br /><applet load="1qt3" size=" | [[Image:1qt3.jpg|left|200px]]<br /><applet load="1qt3" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="1qt3, resolution 1.85Å" /> | caption="1qt3, resolution 1.85Å" /> | ||
'''T26D MUTANT OF T4 LYSOZYME'''<br /> | '''T26D MUTANT OF T4 LYSOZYME'''<br /> | ||
==Overview== | ==Overview== | ||
In contrast to hen egg-white lysozyme, which retains the | 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 --> His, however, converts T4L from an inverting to a retaining enzyme. It is shown here that the Thr-26 --> 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 --> His mutant proceeds via a covalent intermediate. Further mutations (Glu-11 --> His, Asp-20 --> 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. | ||
==About this Structure== | ==About this Structure== | ||
1QT3 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacteriophage_t4 Bacteriophage t4] with CL and HED as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Lysozyme Lysozyme], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.17 3.2.1.17] Full crystallographic information is available from [http:// | 1QT3 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacteriophage_t4 Bacteriophage t4] with <scene name='pdbligand=CL:'>CL</scene> and <scene name='pdbligand=HED:'>HED</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Lysozyme Lysozyme], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.17 3.2.1.17] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1QT3 OCA]. | ||
==Reference== | ==Reference== | ||
| Line 15: | Line 15: | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Kuroki, R.]] | [[Category: Kuroki, R.]] | ||
[[Category: Matthews, B | [[Category: Matthews, B W.]] | ||
[[Category: Weaver, L | [[Category: Weaver, L H.]] | ||
[[Category: CL]] | [[Category: CL]] | ||
[[Category: HED]] | [[Category: HED]] | ||
[[Category: hydrolase]] | [[Category: hydrolase]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:43:27 2008'' | ||
Revision as of 15:43, 21 February 2008
|
T26D MUTANT OF T4 LYSOZYME
OverviewOverview
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 --> His, however, converts T4L from an inverting to a retaining enzyme. It is shown here that the Thr-26 --> 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 --> His mutant proceeds via a covalent intermediate. Further mutations (Glu-11 --> His, Asp-20 --> 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.
About this StructureAbout this Structure
1QT3 is a Single protein structure of sequence from Bacteriophage t4 with and as ligands. Active as Lysozyme, with EC number 3.2.1.17 Full crystallographic information is available from OCA.
ReferenceReference
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 Thu Feb 21 14:43:27 2008