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Calcium determines the shape of fibrillin
D P Reinhardt1, D E Mechling, B A Boswell
1Shriners Hospital for Children, Portland, Oregon 97201, USA. dpr@shcc.org
The Journal of Biological Chemistry
|March 14, 1997
Summary
Calcium binding significantly alters fibrillin-1 structure. Removal of calcium causes fibrillin-1 to shorten and widen, revealing a more flexible form, while calcium binding stabilizes a rigid, extended structure.
Area of Science:
- Biochemistry
- Structural Biology
- Biophysics
Background:
- Fibrillin-1 is a crucial component of the extracellular matrix.
- Calcium ions are known to influence the structure of various proteins.
Purpose of the Study:
- To investigate the Ca2+-dependent structural changes in fibrillin-1.
- To quantify the impact of Ca2+ on fibrillin-1 length, width, and tertiary structure.
Main Methods:
- Velocity sedimentation analysis of fibrillin-1.
- Rotary shadowing electron microscopy.
- Analytical ultracentrifugation of fibrillin-1 subdomains.
- Circular dichroism spectroscopy.
Main Results:
- Fibrillin-1 exhibited different sedimentation coefficients in Ca2+-bound versus Ca2+-free states.
- Ca2+ removal induced a ~25% shortening and ~13-17% widening of fibrillin-1.
- Analysis of fibrillin-1 subdomains confirmed Ca2+-dependent tertiary structural changes.
- Ca2+-free cbEGF-like repeats showed a 20-30% decrease in length compared to Ca2+-bound forms.
Conclusions:
- Fibrillin-1 undergoes significant Ca2+-dependent structural rearrangements.
- The Ca2+-free form is flexible, whereas the Ca2+-bound form is more extended and rigid.
- These findings provide insights into the dynamic nature of fibrillin-1 in the extracellular matrix.