1QT6

E11H Mutant of T4 Lysozyme

Summary for 1QT6

• Entry DOI: 10.2210/pdb1qt6/pdb
• Related: 1QT3 1QT4 1QT5 1QT7 1QT8 1QTV 1QTZ
• Descriptor: PROTEIN (T4 LYSOZYME), CHLORIDE ION, BETA-MERCAPTOETHANOL, ... (4 entities in total)
• Functional Keywords: hydrolase
• Biological source: Enterobacteria phage T4
• Total number of polymer chains: 1
• Total formula weight: 18786.43

Authors

Kuroki, R.,Weaver, L.H.,Matthews, B.W. (deposition date: 1999-06-30, release date: 1999-07-08, Last modification date: 2024-02-14)

Primary citation

Kuroki, R.,Weaver, L.H.,Matthews, B.W.
Structural basis of the conversion of T4 lysozyme into a transglycosidase by reengineering the active site.
Proc.Natl.Acad.Sci.USA, 96:8949-8954, 1999

PubMed Abstract: 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.

PubMed: 10430876
DOI: 10.1073/pnas.96.16.8949

Experimental method

X-RAY DIFFRACTION (1.9 Å)