SH2 domains and SH3 domains
Located on GRB2 (recruited to membrane, and binds SOS)
SH2- 100 a.a., bind to phosphorylated tyrosines and the 3 amino acids following the T residue.
SH3- 60a.a., binds proline rich target sequences. 2-B-sheets placed at right angles, with binding surface of highly hydrophobic residues; variable loops that flank the pocket determine the binding specificity.