SHC phosphotyrosine-binding (PTB) domain. SHC is a substrate for receptor tyrosine kinases, which can interact with phosphoproteins at NPXY motifs. SHC contains an PTB domain followed by an SH2 domain. PTB domains have a PH-like fold and are found in various eukaryotic signaling molecules. They were initially identified based upon their ability to recognize phosphorylated tyrosine residues In contrast to SH2 domains, which recognize phosphotyrosine and adjacent carboxy-terminal residues, PTB-domain binding specificity is conferred by residues amino-terminal to the phosphotyrosine. More recent studies have found that some types of PTB domains can bind to peptides which are not tyrosine phosphorylated or lack tyrosine residues altogether.