MAP2K1 (MEK1) kinse is a dual-specific protein kinase that functions in mitogen-activated protein kinase (MAPK) cascades, controlling cell growth and differentiation. MAP2K1 is activated by a wide variety of growth factors and cytokines and also by membrane-dependent depolarization and calcium influx. This mutant has been activated by subsituting serines 218 and 222 with aspartic acid to mimic the phosphorylated state.