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Conformational changes in ornithine decarboxylase enable recognition by antizyme
1Department of Biological Sciences, Northern Illinois University, DeKalb 60115.
Biochimica Et Biophysica Acta
|January 19, 1990
Summary
Polyamines regulate ornithine decarboxylase (ODC) degradation via antizyme. ODC conformational changes, influenced by cellular conditions, dictate antizyme binding and subsequent enzyme inactivation.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Ornithine decarboxylase (ODC) is a key enzyme in polyamine synthesis.
- ODC degradation is rapid and polyamine-induced, suggesting regulatory control.
- Antizyme is a known ODC-binding protein implicated in ODC regulation.
Purpose of the Study:
- To investigate the binding of antizyme to ODC under various physiological conditions.
- To understand how cellular states affect the ODC-antizyme interaction and ODC stability.
- To elucidate the initial molecular events triggering ODC degradation.
Main Methods:
- Studying ODC-antizyme complex formation in vitro.
- Analyzing ODC protein in altered physiological states (cold, NaCl, spermidine, coenzyme/substrate deprivation).
- Assessing the impact of ODC covalent modifications (difluoromethylornithine, phosphate) on antizyme sensitivity.
Main Results:
- Cold, NaCl, spermidine, and coenzyme/substrate deprivation enhance ODC-antizyme complex formation.
- These conditions also promote ODC homodimer dissociation, preventing antizyme binding.
- Covalent modification of ODC near the active site increases its sensitivity to antizyme.
Conclusions:
- ODC degradation is initiated by subtle conformational changes in the enzyme.
- These conformational changes facilitate antizyme binding.
- Antizyme binding subsequently leads to ODC inactivation and degradation.