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Single site proteolysis in silkworm antitrypsin causes structural changes in behavior against denaturing reagents
T Sasaki1, A Kohara, T Shimidzu
1Department of Food Science and Technology, School of Agriculture, Nagoya University, Japan.
Agricultural and Biological Chemistry
|January 1, 1990
Summary
Silkworm antitrypsin (sw-AT) becomes highly stable after chymotryptic cleavage. This structural change enhances resistance to denaturation and proteolysis, revealing a novel stabilization mechanism.
Area of Science:
- Biochemistry
- Protein structure and stability
Background:
- Silkworm antitrypsin (sw-AT) was traditionally classified within the serpin family.
- Serpins are known for their dynamic structures and roles in regulating proteases.
Purpose of the Study:
- To investigate the effect of specific peptide bond cleavage on the structural stability of silkworm antitrypsin.
- To understand the mechanism behind the observed changes in sw-AT behavior.
Main Methods:
- Chymotryptic cleavage of sw-AT at the Tyr-Val bond.
- Denaturation assays using heat, sodium dodecyl sulfate, and guanidine hydrochloride.
- Circular dichroism spectroscopy to assess structural changes.
- Protease digestion assays using S. aureus V8 protease.
Main Results:
- Chymotryptic cleavage induced significant resistance to denaturation in sw-AT.
- Modified sw-AT exhibited altered circular dichroism spectra, indicating a structural transition.
- The modified sw-AT became resistant to S. aureus V8 protease digestion.
- Stabilization was partly attributed to interactions between the 5 kDa COOH-terminal and 36 kDa NH2-terminal fragments.
Conclusions:
- Cleavage of a single peptide bond in sw-AT triggers a transition from an unstable to a stable structural state.
- This stabilization mechanism involves inter-fragment interactions within the modified protein.
- The findings offer new insights into serpin structural dynamics and stability.