This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
1qt4
From Proteopedia
| Line 1: | Line 1: | ||
[[Image:1qt4.jpg|left|200px]] | [[Image:1qt4.jpg|left|200px]] | ||
| - | + | <!-- | |
| - | + | The line below this paragraph, containing "STRUCTURE_1qt4", creates the "Structure Box" on the page. | |
| - | + | You may change the PDB parameter (which sets the PDB file loaded into the applet) | |
| - | + | or the SCENE parameter (which sets the initial scene displayed when the page is loaded), | |
| - | + | or leave the SCENE parameter empty for the default display. | |
| - | | | + | --> |
| - | | | + | {{STRUCTURE_1qt4| PDB=1qt4 | SCENE= }} |
| - | + | ||
| - | + | ||
| - | }} | + | |
'''T26Q MUTANT OF T4 LYSOZYME''' | '''T26Q MUTANT OF T4 LYSOZYME''' | ||
| Line 29: | Line 26: | ||
[[Category: Matthews, B W.]] | [[Category: Matthews, B W.]] | ||
[[Category: Weaver, L H.]] | [[Category: Weaver, L H.]] | ||
| - | [[Category: | + | [[Category: Hydrolase]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 06:40:38 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 03:40, 3 May 2008
T26Q MUTANT OF T4 LYSOZYME
Overview
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
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 Sat May 3 06:40:38 2008
