Conformational isomerism can limit antibody catalysis
Erik W Debler1, Roger Müller, Donald Hilvert
1Department of Molecular Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
The Journal of Biological Chemistry
|April 18, 2008
Summary
Engineered antibody 34E4 has two active site shapes, limiting its catalytic efficiency. Stabilizing the substrate-binding conformation could enhance its performance in chemical reactions.
Area of Science:
- Protein engineering
- Biocatalysis
- Structural biology
Background:
- Ligand binding often induces protein conformational changes.
- The impact of these changes on engineered catalytic antibodies is less understood.
- Antibody 34E4 catalyzes benzisoxazole to salicylonitrile conversion.
Purpose of the Study:
- Investigate the active-site conformations of antibody 34E4.
- Determine how these conformations affect substrate binding and catalysis.
- Identify limitations to antibody 34E4's catalytic efficiency.
Main Methods:
- X-ray crystallography to visualize active-site structures.
- Pre-steady state kinetic analyses to study reaction mechanisms.
- Characterization of antibody 34E4's conformational dynamics.
Main Results:
- Antibody 34E4 exists in two interconverting active-site conformations.
- A predominant inactive conformation blocks substrate access via Trp(L91).
- Slow isomerization to an active conformation enables substrate binding and catalysis by Glu(H50).
Conclusions:
- Antibody 34E4's catalytic efficiency is limited by its active site's conformational plasticity.
- Stabilizing the active conformation is a potential strategy for improving antibody catalysis.
- This finding may apply to other engineered proteins with conformational limitations.
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