Figure 4.

Initial rate enhancement (v_pY/v_Y) for the SH2-mediated reaction depends on both the density of substrate (A) and the pY ligand (B). (A) A series of monolayers having a fixed density of the pY peptide ligand of 12% and densities of substrate varying from 1% to 12% was treated with the Cut−SH2 fusion protein. The plot shows the initial rate enhancement for each substrate density. (B) The second experiment used a series of monolayers having a constant density of substrate of 12% and densities of the pY ligand ranging from 0% to 12%. Again, the plot shows the initial rate enhancement for each monolayer. Error bars represent the average of three measurements ± one standard deviation.