The transforming protein P68gag-ros of avian sarcoma virus UR2 is a transmembrane protein with the gag portion protruding extracellularly.
We examined the topography of P68gag-ros on the plasma membrane of UR2-transformed chicken embryo fibroblasts. First, radioiodination of intact UR2-transformed cells resulted in the labelling of P68. Second, immunofluorescence experiments showed that anti-p19 antibody, but not an anti-ros serum, stained nonpermeablized UR2-transformed nonproducer cells. Furthermore, protease digestion of intact UR2-transformed cells removed the putative extracellular domain (the p19 portion in P68gag-ros), leaving peptide fragments (p48/p46) which conformed to the size of the ros-encoded sequence in P68. Greater than 60% of P68 molecules were accessible to protease digestion. Based on these results, we conclude that P68gag-ros is a transmembrane protein located primarily on the plasma membrane of UR2-transformed cells. The p19 portion is exposed extracellularly while the kinase domain of ros lies within the cell.
Jong
S M
SM
Rockefeller University, New York, New York 10021.
Wang
L H
LH
D000818:Animals; D001358:Avian Sarcoma Viruses / Q000235:genetics*; D002462:Cell Membrane / Q000648:ultrastructure; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D002645:Chickens; D015683:Gene Products, gag; D007158:Immunologic Techniques; D008562:Membrane Glycoproteins / Q000502:physiology*; D008970:Molecular Weight; D009856:Oncogene Proteins, Viral / Q000502:physiology*; D009857:Oncogenes; D010750:Phosphoproteins / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D012191:Retroviridae Proteins / Q000502:physiology*; D014760:Viral Fusion Proteins / Q000502:physiology*
D015683:Gene Products, gag; D008562:Membrane Glycoproteins; D009856:Oncogene Proteins, Viral; D010750:Phosphoproteins; D012191:Retroviridae Proteins; D014760:Viral Fusion Proteins; D011505:Protein-Tyrosine Kinases