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[Conformational changes of spin-labeled native and modified phosphorylase B].
Biokhimiia (Moscow, Russia)
|March 1, 1980
Summary
Spin labeling studies reveal that glucose-6-phosphate induces conformational changes in phosphorylase B, affecting enzyme mobility. These findings highlight the role of AMP and its phosphate group in active site formation.
Area of Science:
- Biochemistry
- Biophysics
- Enzymology
Context:
- Phosphorylase B is a key enzyme in glycogen metabolism.
- Spin labeling is a technique used to study protein dynamics and structure.
- Understanding enzyme conformational changes is crucial for elucidating catalytic mechanisms.
Purpose:
- To investigate the conformational dynamics of phosphorylase B using spin-labeled derivatives.
- To examine the effects of ligands such as AMP and glucose phosphates on enzyme mobility.
- To elucidate the role of specific functional groups in enzyme-ligand interactions.
Summary:
- Spin-labeled phosphorylase B (phosphorylase I and II) demonstrated differential label mobility, with label I showing greater mobility.
- The enzyme's SH-groups were modified without affecting activity; ligand binding (especially glucose-6-phosphate) induced spectral changes indicating altered spin rotation.
- An S-shaped dependence of label mobility on glucose-6-phosphate concentration was observed, suggesting cooperative binding or conformational transitions, and implicating AMP and its phosphate in active site formation.
Impact:
- Provides insights into the allosteric regulation of phosphorylase B.
- Demonstrates the utility of EPR spin labeling for probing enzyme conformational changes.
- Suggests a mechanism for how AMP and glucose-6-phosphate modulate enzyme activity through structural rearrangements.