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Inactivation of detergent-solubilized sarcoplasmic reticulum ATPase
1Max-Planck-Institut für Medizinische Forschung, Heidelberg, Federal Republic of Germany.
European Journal of Biochemistry
|March 1, 1988
Summary
Detergents rapidly inactivate sarcoplasmic ATPase. Calcium ions (Ca2+) stabilize the enzyme by binding with high affinity, while magnesium ions (Mg2+) offer weaker protection, with effects varying by detergent.
Area of Science:
- Biochemistry
- Enzymology
- Membrane Proteins
Background:
- Sarcoplasmic ATPase is crucial for muscle contraction.
- Understanding its stability in solubilized states is key to studying its function.
- Detergents are often used to solubilize membrane proteins but can affect their activity.
Purpose of the Study:
- To investigate the inactivation of solubilized sarcoplasmic ATPase.
- To compare the effects of different detergents on enzyme stability.
- To analyze the stabilizing roles of Ca2+, Mg2+, and glycerol.
Main Methods:
- Studied sarcoplasmic ATPase inactivation in solution.
- Compared three detergents: C12E8, 1-O-tetradecylpropanediol-(1,3)-3-phosphorylcholine, and myristoylglycerophosphocholine.
- Kinetically analyzed the stabilizing effect of Ca2+ and Mg2+.
Main Results:
- All tested detergents rapidly decreased dinitrophenyl phosphatase activity.
- Ca2+ significantly stabilized the enzyme, with high-affinity binding (apparent affinity constants ~10^6 M-1).
- Mg2+ provided weaker protection (apparent affinity constants ~1 mM-1), with stoichiometry dependent on the detergent.
Conclusions:
- Detergent-mediated inactivation of sarcoplasmic ATPase is rapid.
- High-affinity Ca2+ binding is essential for enzyme stabilization.
- Mg2+ offers less protection, and its effect is detergent-dependent.