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Published on: August 20, 2014
Structural changes to ribonuclease A and their effects on biological activity
J Soucek1, R T Raines, M Haugg
1Department of Cell Physiology, Institute of Hematology and Blood Transfusion, Prague, Czech Republic. souc@uhkt.cz
Summary
Bovine seminal ribonuclease (BS RNase) has immunosuppressive and antitumor effects, unlike bovine pancreatic ribonuclease (RNase A). Researchers created RNase A variants to understand BS RNase
Area of Science:
- Biochemistry
- Molecular Biology
- Immunology
Background:
- Bovine seminal ribonuclease (BS RNase) exhibits immunosuppressive and antitumor activities, while bovine pancreatic ribonuclease (RNase A) lacks cytotoxicity.
- Understanding the mechanism behind BS RNase's cytotoxicity is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the structure-activity relationships of BS RNase and RNase A by creating and analyzing various mutants and hybrid proteins.
- To identify specific amino acid residues and structural features responsible for the unique biological activities of BS RNase.
Main Methods:
- Construction and characterization of RNase A variants with substitutions from BS RNase, including quaternary structure modifications (dimer formation).
- Analysis of hybrid enzymes (SRA 1-5) with segments of RNase A introduced into BS RNase.
- Evaluation of immunosuppressive and antitumor activities of the engineered RNase variants and hybrids.
Main Results:
- A dimeric variant (TM) showed enhanced activity compared to RNase A but less than BS RNase.
- Specific substitutions in RNase A enhanced immunosuppressive activity but not antitumor effects.
- Variant T13, with multiple substitutions, demonstrated the most potent combined immunosuppressive and antitumor effects among RNase A variants.
- Hybrid enzymes (SRA 1-5) retained BS RNase's immunosuppressive activity, but substitutions at positions 111, 113, and 115 in SRA 5 significantly reduced antitumor activity.
- Loss of catalytic and biological activities was observed upon replacement of active-site histidine residues.
Conclusions:
- Specific amino acid residues and quaternary structure play critical roles in the distinct biological activities of BS RNase.
- Residues at positions 111, 113, and 115 are particularly important for the antitumor efficiency of BS RNase.
- The findings suggest potentially different mechanisms of action for RNases on tumor cells and lymphocytes.
Keywords:
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