WT and mutants, H282A and K21A, of α-CaMKII expressed with N-terminal GFP fusions in HEK-293 cells were used for the experiments. A, C and E: The time course of dephosphorylation of WT, H282A and K21A in presence of GST-S1303A-GluN2B or GST-S1291A-GluN2A at 5, 10 and 15 minutes. Phosphorylation intensity without PP1 at 0 time was taken as 100%. The values plotted were from the densitometric data of autoradiographic images as shown in S5 Fig, from three experiments. B, D and F: The slope values of the plots of the time course of dephosphorylation in presence of GluN2B and GluN2A sequences are presented as the bar graphs. (For B and F, p<0.05 in a two-tailed student’s t-test)