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Solution structure of human saposin C in a detergent environment
Cheryl A Hawkins1, Eva de Alba, Nico Tjandra
1Laboratory of Biophysical Chemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, 50 Center Drive, Bethesda, MD 20892, USA.
Journal of Molecular Biology
|February 17, 2005
Summary
Saposin C, a protein crucial for breaking down lipids, adopts an open, membrane-bound structure when interacting with detergents. This reveals its atomic-level details and hydrophobic pocket, unlike its compact form without detergents.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Medicine
Background:
- Saposin C is a lysosomal protein essential for lipid hydrolysis.
- It functions as an activator for the enzyme glucocerebrosidase.
- Understanding its membrane-bound state is critical for elucidating its function.
Purpose of the Study:
- To determine the three-dimensional solution structure of saposin C when bound to a membrane-mimicking detergent, sodium dodecyl sulfate (SDS).
- To provide the first atomic-level representation of membrane-bound saposin C.
- To compare this structure with its previously determined structure in the absence of SDS.
Main Methods:
- High-resolution Nuclear Magnetic Resonance (NMR) spectroscopy was employed.
- The study focused on saposin C in the presence of sodium dodecyl sulfate (SDS).
Main Results:
- Saposin C adopts an open conformation with an exposed hydrophobic pocket when interacting with SDS.
- This contrasts with its compact, non-exposed hydrophobic core structure in the absence of SDS.
- NMR data confirmed SDS molecule interaction with the hydrophobic pocket of saposin C.
Conclusions:
- The determined structure represents the first atomic-level view of membrane-bound saposin C.
- The open conformation with an exposed hydrophobic pocket is key to its membrane interactions.
- Structural similarities were noted between membrane-bound saposin C and saposin B, suggesting potential shared lipid-interaction mechanisms.