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Crystal structure of a caricain D158E mutant in complex with E-64
N A Katerelos1, M A Taylor, M Scott
1Institute of Food Research, Reading Laboratory, UK.
FEBS Letters
|August 19, 1996
Summary
The D158E mutant of caricain, a protease, was studied in complex with E-64. Researchers found that a small structural expansion allowed glutamate to form the same hydrogen bonds as aspartate in the native enzyme, explaining altered activity.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Caricain, also known as papaya protease omega, is a key cysteine protease.
- Understanding enzyme structure-activity relationships is crucial for drug design and biochemical research.
Purpose of the Study:
- To determine the high-resolution crystal structure of the D158E mutant of caricain in complex with E-64.
- To investigate the structural basis for the altered activity observed in the D158E mutant.
Main Methods:
- X-ray crystallography was employed to determine the structure.
- The structure was solved at 2.0 Å resolution with an R factor of 19.3%.
Main Results:
- The D158E mutant structure revealed that the introduced glutamate residue forms identical hydrogen bonds as the aspartate in the native caricain structure.
- Despite predictions of steric hindrance, the glutamate side chain is accommodated through a local expansion of the protein structure.
- This structural adaptation directly correlates with the observed changes in enzyme activity.
Conclusions:
- Small, localized structural adjustments in proteins can accommodate significant amino acid substitutions.
- The study elucidates the mechanism by which the D158E mutation alters caricain activity, highlighting the interplay between structure and function.