Src homology (SH2) domains promote the formation of protein complexes through their interaction with specific phosphotyrosine (pY)-containing motifs in their binding partners, thus playing and important role in the regulation of numerous signaling pathways. SH2 domains demonstrate a primary binding-sequence specificity of about five amino acids in their partners, pY-2 through to pY+ 3, with pY being the zeroth position. The binding specificities of SH2-B1β and SH2-B3 SH2 domains were determined using a “one-bead-one compound” combinatorial peptide library method. The beads that bear the tightest binding pY peptide sequences against the SH2 domains are selected by an enzyme-linked assay or fluorescence and individually sequenced by a partial Edman degradation/mass spectrometry method.
The adaptor proteins, SH2-B1β and SH2-B3 (also known as SH2-Bβ and LnK respectively), are two members of a Src homology-2 (SH2) domain subfamily that modulate protein tyrosine kinases signaling. This thesis demonstrates that the binding motifs of SH2-B1β and SH2-B3 can be determined via combinatorial chemistry. The binding motif for SH2 B1β is XXpY[E/Y/Abu]XL and for SH2-B3 is XXpYVXL. Database searches and validation of new physiological partners of SH2-B1β and SH2-B3 will be useful to determine the function of these proteins.