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Structural constraints on protein self-processing in L-aspartate-alpha-decarboxylase.
Florian Schmitzberger1, Mairi L Kilkenny, Carina M C Lobley
1Department of Biochemistry, 80 Tennis Court Road, Cambridge CB2 1GA, UK. florian@cryst.bioc.cam.ac.uk
The EMBO Journal
|November 25, 2003
Summary
Aspartate decarboxylase self-cleavage involves specific conformational changes. Stabilization of the oxyoxazolidine intermediate is crucial for this enzyme
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Aspartate decarboxylase is synthesized as a pro-protein.
- This precursor undergoes intramolecular self-cleavage at the Gly24-Ser25 site.
Purpose of the Study:
- To elucidate the molecular mechanism of aspartate decarboxylase self-processing.
- To determine the structural basis for the enzyme's intramolecular cleavage.
Main Methods:
- Crystal structure determination of the native precursor and various mutants.
- Comparative structural analysis of the cleavage site.
Main Results:
- Identified specific conformational constraints governing self-processing.
- Proposed a catalytic mechanism involving Thr57 and a water molecule stabilizing an oxyoxazolidine intermediate.
- Highlighted the role of conformational flexibility in the preceding loop.
Conclusions:
- The mechanism emphasizes stabilization of the oxyoxazolidine intermediate.
- Structural similarities exist with other self-processing systems.
- Mutant studies alone (e.g., Ser-->Ala) may misinterpret the mechanism.