PTB do iE a new protehl mp kaed in signg tr uctio11

SE~ PROTE~I #O~N5 have been identified that feature in the assembly of ~igna~ transduction coro- plexes following activation of receptor tyrosine kinases (RTKs). Src homology 2 (SH2) domains, which are found in a plethora og signalling proteins, bind phosphorylated tyrosine residues in the context of amino acids carboxy- terminal to the phosphotyrosine, while Src homology 3 (SHJ) domains, originally noted as regions of homology between Src, Crk and PLCT, b~nd Pro-rich sequence¢. Pleckstrin-homology (PH) domains, present in a variety of membrane-associated proteins, several of which also contain SH2 and SH3 domains, are thought to play a role in protein-protein or protein-lipid inter- actions. Here, we summarize recent evidence for the existence of a new phosphotyrosine-binding (PTB) domain present in the Shc adaptor protein that appears to mediate protein-protein interactions. One of the notable features of the PTB domain is that aRhough, like the SH2 domain, it