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Cholesterol interaction with recombinant human sterol carrier protein-2
S M Colles1, J K Woodford, D Moncecchi
1Department of Pharmacology and Cell Biophysics, University of Cincinnati Medical Center, Ohio 45267-0004, USA.
Lipids
|September 1, 1995
Summary
Sterol carrier protein-2 (SCP-2) binds sterols with high affinity, suggesting a role in lipid transport. This protein shields its tryptophan residue from water when bound to cholesterol, indicating a specific binding site.
Area of Science:
- Biochemistry
- Molecular Biology
- Lipid Metabolism
Background:
- Sterol carrier protein-2 (SCP-2) is involved in intracellular sterol transport.
- Understanding SCP-2's sterol binding properties is crucial for elucidating its function in lipid homeostasis.
Purpose of the Study:
- To investigate the binding affinity and characteristics of human recombinant SCP-2 for sterols.
- To characterize the structural changes in SCP-2 upon sterol binding.
Main Methods:
- Ligand binding assays using [3H]cholesterol and Lipidex 1000.
- Fluorescent dehydroergosterol binding assay.
- Phase fluorometry and circular dichroism spectroscopy.
Main Results:
- SCP-2 exhibited high affinity for cholesterol (Kd = 0.3 microM) and dehydroergosterol (Kd = 1.7 microM), with a single binding site.
- Sterol binding shielded the SCP-2 tryptophan residue from solvent exposure.
- Cholesterol binding induced a decrease in SCP-2's alpha-helical content and rotational correlation time.
Conclusions:
- SCP-2 binds sterols with high affinity, consistent with its role as a lipid transfer protein.
- The binding mechanism involves conformational changes and shielding of the tryptophan residue.
- SCP-2 may function as an aqueous carrier or at membrane surfaces to facilitate sterol transport.