Characterization of pp85, a Target of Oncogenes and Growth Factor Receptors

Bruce Cohen, Yuxi Liu, Brian Druker, Thomas M. Roberts, Brian S. Schaffhausen

Research output: Contribution to journalArticlepeer-review

63 Scopus citations


An 85,000-molecular-weight polypeptide (85K polypeptide) has previously been identified as a common substrate for tyrosine phosphorylation upon polyomavirus middle T transformation or upon platelet-derived growth factor stimulation of 3T3 cells. In each case, pp85 has an associated phosphatidylinositol kinase activity. The tissue distribution of pp85 was determined by middle T blotting experiments; the highest levels were found in brain, lung, and spleen tissues. High-resolution examination of 85K by isoelectric focusing demonstrated that there are at least 10 different forms. These were resolved into two families, 85K and 86K; the ratio of the two families changed in different cells. Similar forms were found for pp85 associated with pp60v-src. Individual species within each family differed by phosphorylation. Analysis of pp85 and pp86 by immunoprecipitation with anti-phosphotyrosine antibody showed increasing phosphorylation in response to middle T or pp60v-src transformation. The association of middle T with pp85 and pp60c-src was examined in pulse-chase experiments. Association of middle T with pp60c-src was slow and was accompanied by progressive modification of middle T. pp85 formed a dissociable complex with middle T within 2.5 min.

Original languageEnglish (US)
Pages (from-to)2909-2915
Number of pages7
JournalMolecular and cellular biology
Issue number6
StatePublished - Jun 1990
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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