MAP2K4 Polyclonal Antibody for Western Blot MAP2K4 (MEK4) serine/threonine kinase (mitogen-activated protein kinase 4) MEK4 or MKK4 is a dual specificity kinase of the STE7 family that phosphorylates and activates JNK1 and -2 as well as p38. MAP2K4 prefe