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Calcium binding sequences in calmyrin regulates interaction with presenilin-2
Jingsong Zhu1, Stacy M Stabler, James B Ames
1Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD 21201, USA.
Experimental Cell Research
|October 12, 2004
Summary
Calmyrin acts as a calcium sensor, with its EF-hands 3 and 4 binding calcium and mediating interaction with presenilin-2 (PS2). Both calcium binding and myristoylation are crucial for calmyrin
Area of Science:
- Molecular and Cellular Biology
- Biochemistry
- Protein-Protein Interactions
Background:
- Calmyrin is a myristoylated calcium-binding protein with four EF-hands.
- Calmyrin interacts with proteins like presenilin-2 (PS2).
- The biophysical properties and regulatory mechanisms of calmyrin binding are poorly understood.
Purpose of the Study:
- To elucidate the biophysical properties of calmyrin.
- To understand the molecular mechanisms regulating calmyrin's interactions.
- To investigate the roles of calcium binding and myristoylation in calmyrin function and localization.
Main Methods:
- Site-directed mutagenesis and Ca2+ binding studies.
- Spectroscopic techniques (UV, CD) and NMR spectroscopy.
- Yeast two-hybrid assays, pulse-chase studies, and immunofluorescence microscopy in HeLa cells.
Main Results:
- Calmyrin binds two Ca2+ ions via EF-hands 3 and 4 (Kd ≈ 53 µM).
- Ca2+-free and -bound calmyrin exhibit distinct conformations.
- Intact EF-hands 3 and 4 are essential for PS2 interaction; calcium binding, not myristoylation, affects PS2 colocalization.
Conclusions:
- Calmyrin functions as a calcium sensor.
- Calcium binding to EF-hands 3 and 4 is critical for calmyrin's interaction with the PS2 loop.
- Both calcium binding and myristoylation influence calmyrin's intracellular targeting and stability.