title: In vivo tyrosine phosphorylations of the Abelson virus transforming protein are absent in its normal cellular homolog.
abstract: The transforming gene product of the Abelson murine leukemia virus (A-MuLV) is a phosphoprotein encoded by combined viral and cellular sequences. Previous work has shown the existence of a serologically crossreactive normal cellular phosphoprotein called NCP150. We have utilized two-dimensional phosphopeptide mapping and phosphoamino acid analysis to compare the structures of NCP150 and wild-type and mutant forms of the A-MuLV protein labeled in vivo with 32P-orthophosphate. This analysis demonstrated clear homology between NCP150 and wild-type A-MuLV protein, but a number of phosphorylation differences were seen. Among them, two specific tyrosine phosphorylations present in all transformation-competent Abelson proteins were not observed in NCP150. No other phosphotyrosine-containing peptides were detected. In addition, transformation-defective mutants isolated from either the P120 or P160 wild-type strain lack phosphotyrosine-containing peptides. Double-infection studies with such transformation-defective and transformation-competent A-MuLV strains show that Abelson viral proteins may be substrates for their own tyrosine-specific kinase activity in vivo. These observations suggest that the phosphotyrosine kinase activity of the abl region may be controlled, and may function, differently in its viral and cellular forms.
mesh_terms: D000011:Abelson murine leukemia virus / Q000502:physiology*; D000818:Animals; D002472:Cell Transformation, Viral; D003429:Cross Reactions; D009052:Leukemia Virus, Murine / Q000502:physiology*; D051379:Mice; D009857:Oncogenes; D010766:Phosphorylation; D019000:Phosphotyrosine; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D019000:Phosphotyrosine; D014443:Tyrosine