Differential subcellular localization of in vivo-phosphorylated and nonphosphorylated middle-sized tumor antigen of polyoma virus and its relationship to middle-sized tumor antigen phosphorylating activity in vitro.

Abstract

A small fraction of polyoma virus middle-sized tumor (T) antigen is phosphorylated in vivo, resulting in a small amount of phosphotyrosine and phosphothreonine and significantly larger amounts of phosphoserine. When infected cells are separated into nuclear, plasma membrane, and low-speed supernatant fractions, 80-95% of in vivo-phosphorylated middle-sized T antigen is localized to the plasma membrane fraction, while 25-50% of [35S]methionine-labeled middle-sized T antigen is found in the nuclear fraction and the same amount is found in the plasma membrane fraction. Immunoprecipitated T antigens contain a protein kinase activity that phosphorylates middle-sized T antigen at tyrosine residues. Eighty to 90% of this activity is located in the plasma membrane fraction. When immunoprecipitated T antigens are treated with alkaline phosphatase, middle-sized T antigen-phosphorylating activity decreases as 32PO4 is lost from in vivo 32P-labeled middle-sized T antigen. The possibility that in vivo-phosphorylated middle-sized T antigen located in the plasma membrane is an active tyrosine-specific kinase is discussed.

• Authors: K Segawa, Y Ito
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 79 Issue 22 Pg. 6812-6 (Nov 1982) ISSN: 0027-8424 [Print] United States
• PMID: 6294653 (Publication Type: Journal Article)

Chemical References

• Amino Acids
• Antigens, Viral
• Antigens, Viral, Tumor
• Protein Kinases
• Alkaline Phosphatase

Topics

• Alkaline Phosphatase
• Amino Acids (analysis)
• Animals
• Antigens, Viral (analysis, isolation & purification)
• Antigens, Viral, Tumor
• Cells, Cultured
• Mice
• Molecular Weight
• Phosphorylation
• Polyomavirus (enzymology, immunology)
• Protein Kinases (metabolism)