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Crystal structure of selenosubtilisin at 2.0-A resolution
1Department of Chemistry, Scripps Research Institute, La Jolla, California 92037.
Biochemistry
|June 22, 1993
Summary
The structure of selenosubtilisin, a modified protease, reveals how selenium incorporation affects enzyme activity. This artificial selenoenzyme
Area of Science:
- Biochemistry
- Structural Biology
- Enzyme Engineering
Background:
- Subtilisin is a bacterial serine protease.
- Selenocysteine replaces the active site serine in selenosubtilisin.
- Selenium's unique chemical properties influence enzyme function.
Purpose of the Study:
- Determine the three-dimensional structure of selenosubtilisin.
- Understand how selenium modification impacts enzyme active site and properties.
- Compare selenosubtilisin with natural selenoenzymes.
Main Methods:
- X-ray crystallography at 2.0-A resolution.
- Molecular replacement technique.
- Chemical modification of subtilisin.
Main Results:
- The selenium moiety is in the seleninic acid oxidation state at residue 221.
- Key active site interactions (His64-Asp32) are maintained.
- Hydrogen bonds stabilize the seleninic acid group, explaining its low pKa and reactivity.
- Protein backbone structure is largely unchanged from native subtilisin.
Conclusions:
- The structure of selenosubtilisin provides insights into selenium's role in enzyme catalysis.
- Chemical modification is a viable strategy for creating novel enzyme variants.
- Structural comparison aids in understanding the diverse functions of selenium in enzymes.