 Grb2 has two closely related proteins with similar domain organizations, Gads and Grap.Gads and Grap are expressed specifically in hematopoietic cells and function in the coordination of tyrosine kinase mediated signal transduction.The SH2 domain of Grb2 binds to phosphorylated tyrosine-containing peptides on receptors or scaffold proteins with a preference for pY-X-N-X, where X is generally a hydrophobic residue such as valine (see ).