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Degradation of a cAMP-binding protein is inhibited by human c-Ha-ras gene products
Abstract:
Incubation of the particulate fraction of cell extract prepared from NIH3T3 mouse fibroblasts resulted in preferential proteolytic degradation of a cAMP-binding protein. The proteolysis was inhibited by human c-Ha-ras gene products produced by Escherichia coli. The proteolysis was observed at pH 6 to 7, and inhibited by antipain and leupeptin. These results suggest that cAMP-binding proteins might be cleaved by thiol proteinases. In fact, c-Ha-ras gene products were proved to inhibit the cathepsin B-like activity present in the particulate fraction.
Insights
Human c-Ha-ras gene products inhibit the breakdown of cyclic adenosine monophosphate (cAMP)-binding proteins by blocking thiol proteinase activity in mouse fibroblast cell extracts.
Area of Science:
- Molecular Biology
- Biochemistry
- Cell Biology
Background:
- Cyclic adenosine monophosphate (cAMP)-binding proteins play crucial roles in cellular signaling.
- NIH3T3 mouse fibroblasts are a common model system for studying cellular processes.
- Proteolytic degradation can impact protein function and cellular regulation.
Purpose of the Study:
- To investigate the proteolytic degradation of cAMP-binding proteins in NIH3T3 mouse fibroblasts.
- To determine the effect of human c-Ha-ras gene products on this degradation process.
- To identify the type of proteinase involved and its activity.
Main Methods:
- Incubation of particulate fractions from NIH3T3 mouse fibroblast cell extracts.
- Assay for proteolytic degradation of cAMP-binding proteins.
- Testing the inhibitory effects of human c-Ha-ras gene products.
- Enzyme inhibition assays using antipain and leupeptin.
- Characterization of cathepsin B-like activity.
Main Results:
- Preferential proteolytic degradation of a cAMP-binding protein was observed.
- Human c-Ha-ras gene products significantly inhibited this proteolysis.
- The degradation occurred optimally at pH 6-7 and was inhibited by antipain and leupeptin.
- These findings suggest the involvement of thiol proteinases.
- c-Ha-ras gene products were shown to inhibit cathepsin B-like activity.
Conclusions:
- cAMP-binding proteins are susceptible to degradation by thiol proteinases.
- Human c-Ha-ras gene products possess inhibitory activity against these proteinases, specifically cathepsin B-like enzymes.
- This interaction highlights a potential regulatory mechanism involving c-Ha-ras in controlling cAMP-binding protein stability.