Figure 1: Treatment of NIH/3T3 cells with PMA stimulates phosphorylation of MEK1 at Ser217/221, detected by PathScan® Phospho-MEK1 (Ser217/221) Sandwich ELISA kit #7175, but does not affect the level of total MEK1 protein detected by PathScan® Total MEK1 Sandwich ELISA kit #7165. Lambda protein phosphatase (LPP) treatment of control cell lysates (37ºC for 90 minutes) abolished the basal phosphorylation of MEK1 in control lysates shown in both Sandwich ELISA and Western analysis. The OD450 readings are shown in the top figure, while the corresponding Western blot, using Phospho-MEK1/2 (Ser217/221) Antibody #9121 (right panel) or MEK1 Mouse mAb #2352 (left panel), is shown in the bottom figure.