Related Experiment Videos
Changes in structure and stability of calbindin-D(28K) upon calcium binding
Sergei Yu Venyaminov1, Elena S Klimtchuk, Zeljko Bajzer
1Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA. venyaminov.sergei@mayo.edu
Analytical Biochemistry
|October 7, 2004
Summary
Calcium binding significantly alters the tertiary structure and thermal stability of calbindin-D(28K), a protein vital for neural function and calcium transport. Secondary structure remains largely unaffected by calcium ions.
Area of Science:
- Biochemistry
- Molecular Biology
- Biophysics
Background:
- Calbindin-D(28K) is crucial for neural function and calcium transport in the intestine and kidney.
- Understanding calcium binding is key to elucidating its biological roles.
Purpose of the Study:
- To investigate the structural and stability changes in calbindin-D(28K) upon calcium binding.
- To characterize the calcium-binding sites and their affinities.
Main Methods:
- Fluorescence spectroscopy was used to monitor Ca(2+) titration.
- Circular dichroism (CD) spectroscopy (far-UV and near-UV) assessed structural changes.
- Thermostability was evaluated through heat denaturation studies.
Main Results:
- Two classes of calcium-binding sites were identified with high affinities (approx. 10^7.5 and 10^8.9 M⁻¹).
- Near-UV CD spectra indicated significant changes in tertiary structure upon calcium addition, particularly between pCa 7.0 and 8.0.
- Far-UV CD spectra showed minimal alterations in secondary structure.
- Protein thermostability correlated with near-UV CD spectral changes.
Conclusions:
- Calcium binding primarily affects the local tertiary structure around aromatic residues and enhances the thermal stability of calbindin-D(28K).
- Secondary structure is largely insensitive to calcium ions.
- The apo-state denaturation suggests weakly interacting domains with similar thermodynamic properties.