MBP and Biotinylated MBP was phosphorylated with 0.05ug of active ERK1 with P 32 radiolabeled ATP. Assay reference: Sanghera JS et al., J Immunol. (1996) 156:4457-4465 Activity of biotinylated MBP Lane a (5 ug of biotinylated MBP): 33682 counts/min Lane b (2.5 ug of biotinylated MBP): 18478 counts/min Lane c (1.25 ug of biotinylated MBP): 6714 counts/min Lane d (0.625 ug of biotinylated MBP): 2889 counts/min Lane e (0.36 ug of biotinylated MBP): 1039 counts/min Lane f (0.18 ug of biotinylated MBP): 633 counts/min Control Lane (0.0 ug of biotinylated MBP): 145 counts/min Non-biotinylated MBP Activity Lane A (5 ug of biotinylated MBP): 37604 counts/min Lane B (2.5 ug of biotinylated MBP): 17824 counts/min Lane C (1.25 ug of biotinylated MBP): 8867 counts/min Lane D (0.625 ug of biotinylated MBP): 4190 counts/min Lane E (0.36 ug of biotinylated MBP): 2248 counts/min Lane F (0.18 ug of biotinylated MBP): 1500 counts/min Control Lane (0.0 ug of biotinylated MBP): 218 counts/min