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Forms of pp60v-src isolated from Rous sarcoma virus-transformed cells.
Journal of Virology
|May 1, 1987
Summary
Researchers investigated the Rous sarcoma virus transforming protein, pp60v-src, in cancer cells. They found that modifications, not just an electrophoretic variant, regulate its kinase activity, suggesting new regulatory mechanisms.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- An electrophoretic variant of Rous sarcoma virus pp60v-src protein with phosphotyrosine modification was previously linked to increased kinase activity.
- This variant was observed in vanadate-treated src-transformed cells.
Purpose of the Study:
- To investigate the relationship between pp60v-src electrophoretic variants and its kinase activity.
- To resolve different immunologic forms of pp60v-src using a specific monoclonal antibody (MAb).
Main Methods:
- Used a src-specific monoclonal antibody (MAb) to distinguish pp60v-src populations.
- Performed serial immunoprecipitations to isolate four pp60v-src populations.
- Analyzed phosphoamino acid composition, tryptic phosphopeptide profiles, and tyrosyl kinase specific activities.
Main Results:
- Identified four pp60v-src populations with distinct modifications but similar kinase activities.
- Vanadate-treated cells showed enhanced kinase activity in both MAb-reactive and unreactive fractions.
- The MAb-reactive fraction from vanadate-treated cells lacked the variant form but retained enhanced activity.
Conclusions:
- The initial correlation between the electrophoretic variant and increased kinase activity is not supported.
- pp60v-src functional regulation may involve other, yet undefined, modifications.
- This challenges existing models of src protein regulation.