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Secondary structure perturbations in salt-induced protein precipitates
1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125.
Biochimica Et Biophysica Acta
|January 8, 1991
Summary
Precipitating proteins with KSCN salt significantly increases beta-sheet structures while decreasing alpha-helix content. These protein structural changes are linked to primary sequence and surface area, mirroring other aggregation events.
Area of Science:
- Protein biochemistry and structural biology.
- Investigating protein conformational changes.
Background:
- Protein precipitation is influenced by chaotropic and stabilizing salts.
- Understanding secondary structure changes during precipitation is crucial for protein aggregation studies.
Purpose of the Study:
- To investigate the secondary structure alterations of twelve proteins upon precipitation using potassium thiocyanate (KSCN) and sodium sulfate (Na2SO4).
- To correlate these conformational changes with primary, secondary, and tertiary structural elements of native proteins.
Main Methods:
- Analysis of amide I band Raman spectra to estimate alpha-helix and beta-sheet content in native and precipitated proteins.
- Statistical analysis of secondary structure perturbations.
- Quantification of primary (amino acid fractions), secondary (X-ray estimates), and tertiary (dipole moment, solvent-accessible surface area) structures.
Main Results:
- Precipitation with KSCN significantly induced beta-sheet formation and alpha-helix loss.
- Increased beta-sheet content in KSCN precipitates correlated with the fraction of charged amino acids and surface area.
- Changes in alpha-helix content were influenced by native helical content and dipole moment.
Conclusions:
- KSCN-induced precipitation promotes beta-sheet formation, a key event in protein aggregation.
- Protein primary and tertiary structures influence secondary structure changes during precipitation.
- Observed structural changes parallel those in other protein aggregative phenomena.
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