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[Allosteric effect of substrate on sarcoplasmic reticulum Ca-ATPase]
Biokhimiia (Moscow, Russia)
|March 1, 1977
Summary
High concentrations of adenosine triphosphate (ATP) activate sarcoplasmic reticulum Ca-dependent ATPase. This activation is lost upon trypsin treatment or repeated freezing, suggesting an allosteric mechanism involving enzyme conformational changes.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Context:
- Sarcoplasmic reticulum Ca-dependent ATPase (Ca-ATPase) is crucial for muscle calcium regulation.
- Adenosine triphosphate (ATP) is known to influence Ca-ATPase activity.
- Understanding the regulatory mechanisms of Ca-ATPase is vital for cellular physiology.
Purpose:
- To investigate the activating effect of high ATP concentrations on Ca-dependent ATPase from sarcoplasmic reticulum.
- To elucidate the molecular mechanism underlying ATP-induced Ca-ATPase activation.
- To analyze the role of specific protein components and enzyme conformation in ATP's effect.
Summary:
- High ATP concentrations activate Ca-dependent ATPase in both membrane and purified preparations.
- Trypsin treatment abolishes ATP activation, correlating with the degradation of a 100,000 MW protein into 45,000 and 55,000 MW fragments.
- Repeated freezing also eliminates ATP's activating effect, supporting an allosteric model where ATP binding induces conformational changes between two Ca-ATPase states.
Impact:
- Provides insights into the allosteric regulation of Ca-ATPase by ATP.
- Identifies a specific protein component (100,000 MW) critical for ATP-mediated activation.
- Establishes kinetic parameters for different Ca-ATPase conformers, advancing our understanding of enzyme function.