| We also focused on a novel interaction between Hck and ELMO 1 , an 84 kDa protein that was recently identified as the mammalian ortholog of the Caenorhabditis elegans gene , ced 12 . ^^^ Using purified proteins , we confirmed that WASP interacting protein and ELMO 1 interact directly with the SH 3 domain of Hck . ^^^ We also show that Hck and ELMO 1 interact in intact cells and that ELMO 1 is heavily tyrosine phosphorylated in cells that co express Hck , suggesting that it is a substrate of Hck . ^^^ The binding of ELMO 1 to Hck is specifically dependent on the interaction of a polyproline motif with the SH 3 domain of Hck . ^^^ |