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Calcium-dependent self-assembly of human centrin 2.
Martine Tourbez1, Claudia Firanescu, Ao Yang
1INSERM and Institut Curie-Recherche, Centre Universitaire Paris-Sud, 91405 Orsay Cedex, France.
The Journal of Biological Chemistry
|September 10, 2004
Summary
Human centrin 2 (HsCen2) self-assembles in vitro, forming fibers crucial for centrosome structure. The N-terminal fragment is essential for this polymerization, highlighting its role in organizing centrosome components.
Area of Science:
- Biochemistry
- Cell Biology
- Structural Biology
Background:
- Human centrin 2 (HsCen2) is a calcium-binding protein found in centrosomes and basal bodies.
- Centrin-containing fibers connect centrioles, but their molecular basis and role in centrosome duplication are unknown.
Purpose of the Study:
- To investigate the in vitro self-assembly properties of HsCen2.
- To elucidate the structural role of HsCen2 in centrosome organization.
Main Methods:
- Light scattering experiments to study protein polymerization kinetics and equilibrium.
- Use of a hydrophobic fluorescent probe (ANS) to probe protein interactions.
- Isothermal titration calorimetry to analyze N-terminal domain binding.
Main Results:
- HsCen2 undergoes reversible self-assembly in vitro, exhibiting nucleation and elongation steps.
- Polymerization is inhibited by ANS, suggesting interference with nucleation via hydrophobic interactions.
- A truncated form (Delta25HsCen2) lacking the N-terminus does not self-assemble.
- The N-terminal domain binds to Delta25HsCen2 oligomers with significant affinity, driven by entropy.
Conclusions:
- HsCen2 self-assembly is a critical process for forming structural fibers within the centrosome.
- The N-terminal region of HsCen2 plays a vital role in initiating and organizing its polymerization.
- These findings provide insights into the molecular mechanisms underlying centrosome structure and duplication.