FIGURE 3.

CD2 and CD244 intracellular regions show higher affinity for FYN than LCK. Equilibrium binding data from which dissociation constants were calculated were obtained by passing various concentrations of soluble recombinant protein over immobilized peptides. a and b, FYN-SH3-SH2 and LCK-SH3-SH2 binding to proline-rich peptides based on the 2 regions of the human CD2 cytoplasmic region (Table 1). c, the interaction of CMS and FYN-SH3-SH2 (data not shown) with CD2 322 peptide is dependent on aa PR at positions 335–336, which are substituted to AA in the CD2 mutant peptide. d, FYN-SH3-SH2 binds SAP. e and f, FYN SH3-SH2 binds with a higher affinity than LCK-SH3-SH2 to phosphorylated synthetic peptides based on CD244 ITSM-1 and EAT-2 127 (Table 1). Lines show best fits except for CTLA-4 in f.