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Conformational properties of streptokinase
1Department of Chemistry, University of Notre Dame, Indiana 46556.
The Journal of Biological Chemistry
|June 15, 1989
Summary
This study investigated streptokinase (SK) conformational changes using thermal and spectroscopic methods. SK exhibits reversible unfolding in low salt but aggregates irreversibly in high salt, with pH affecting its stability and structure.
Area of Science:
- Biochemistry
- Protein structure and dynamics
Background:
- Streptokinase (SK) is a crucial thrombolytic agent.
- Understanding SK's conformational properties is vital for its therapeutic applications.
Purpose of the Study:
- To characterize the conformational stability and secondary structure of streptokinase (SK).
- To investigate the effects of ionic strength and pH on SK's thermal unfolding.
Main Methods:
- Differential scanning calorimetry (DSC) to assess thermal transitions.
- Circular dichroism (CD) spectroscopy to determine secondary structure.
- Analysis of thermal unfolding properties under varying ionic strength and pH conditions.
Main Results:
- SK shows a reversible two-state thermal transition in low ionic strength buffers.
- In high ionic strength, SK undergoes irreversible aggregation.
- Decreasing pH destabilizes SK, while alkaline pH (8.4-9.4) stabilizes a specific region.
- CD analysis estimates SK secondary structure: 17% alpha-helices, 28% beta-sheet, 21% beta-turns, and 34% disordered structures, indicating an alpha + beta protein.
Conclusions:
- Streptokinase's conformational stability is sensitive to ionic strength and pH.
- SK's structural behavior suggests potential for aggregation under certain conditions.
- The protein's secondary structure is predominantly alpha-helical and beta-sheet, consistent with an alpha + beta protein classification.