MEK2/MAP2K2

Encoded by MAP2K2 on chromosome 19, MEK2 is the close paralog of MEK1 and likewise acts as a dual-specificity kinase that activates ERK1/2 downstream of RAF. The two enzymes share overlapping regulation and substrates yet are not fully redundant: MEK2 shows a distinct tissue expression pattern, genetic studies attribute specific roles to it in cardiac and developmental contexts, and MEK2 knockout mice remain viable. Like MEK1, it is phosphorylated by RAF on two activation-loop serines and is a validated node for oncology drugs. Allosteric MEK1/2 inhibitors such as selumetinib and binimetinib block both paralogs and are used in tumors driven by RAS-RAF pathway activation.