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Two-dimensional crystallization of Ca-ATPase by detergent removal
J J Lacapère1, D L Stokes, A Olofsson
1Institut Curie, Section de Recherche, UMR-CNRS 168, Paris, France. lacapere@curie.fr
Biophysical Journal
|September 3, 1998
Summary
Researchers produced detergent-depleted Ca-ATPase crystals using Bio-Beads. Crystal formation and morphology depend on lipid-to-protein ratio, detergent removal rate, and protein conformation, revealing insights into crystallogenesis.
Area of Science:
- Biochemistry
- Structural Biology
- Membrane Proteins
Background:
- Detergent removal is crucial for crystallizing membrane proteins like Ca-ATPase.
- Understanding Ca-ATPase structure is key to its function in calcium transport.
Purpose of the Study:
- To develop a method for producing detergent-depleted Ca-ATPase crystals.
- To analyze the factors influencing crystal formation and morphology.
- To propose a general model for crystallogenesis of asymmetrical membrane proteins.
Main Methods:
- Using Bio-Beads for detergent removal from purified Ca-ATPase.
- Electron microscopy for analyzing crystal crystallinity and morphology.
- Electron crystallography for determining unit cell parameters and projection maps.
Main Results:
- Crystal formation requires a lipid-to-protein ratio below 0.4 w/w.
- Detergent removal rate dictates crystal morphology: slow removal yields multilamellar sheets, fast removal yields unilamellar tubes.
- Ca2+ is required for tubular and multilamellar crystals; ADP induces different unit cell packing while maintaining bipolar orientation.
Conclusions:
- A model for Ca-ATPase crystallogenesis is proposed, applicable to asymmetrical proteins.
- Crystal morphology is controllable by manipulating detergent removal rates.
- Protein conformation significantly impacts crystal packing and formation.