| In addition to the EGF receptor , PI3K C2beta ( 2 298 ) also isolated both Shc and Grb 2 from A 431 cell lysates . ^^^ Recombinant Grb 2 directly bound PI3K C2beta in vitro , and this effect was reproduced using either SH 3 domain expressed as a glutathione S transferase ( GST ) fusion . ^^^ The relevance of this association was confirmed when PI3K C2beta was isolated by coimmunoprecipitation with anti Grb 2 antibody from numerous cell lines . ^^^ Using immobilized , phosphorylated EGF receptor , recombinant PI3K C2beta was only purified in the presence of Grb 2 . ^^^ We conclude that proline rich motifs within the N terminus of PI3K C2beta mediate the association of this enzyme with activated EGF receptor and that this interaction involves the Grb 2 adaptor . . ^^^ |