MEK1 and MEK2

MEK1 and MEK2, also known as MAP2K1 and MAP2K2, are activated in response to mitogenic stimuli. Activation occurs through dual phosphorylation at S218/S222 of MEK1 and S222/S226 of MEK2 by several upstream MAP3Ks. Both MEK1 and MEK2 are dual-specificity protein kinases, phosphorylating and activating ERK1 and ERK2 at Thr and Tyr positions.