MAP3K1, also named as MAPKKK1, MEKK and MEKK1, belongs to the protein kinase superfamily, STE Ser/Thr protein kinase family and MAP kinase kinase kinase subfamily. MAP3K1 is a component of a protein kinase signal transduction cascade. MAP3K1 activates the ERK and JNK kinase pathways by phosphorylation of MAP2K1 and MAP2K4. It activates CHUK and IKBKB, the central protein kinases of the NF-kappa-B pathway. It catalyzes the reaction: ATP + a protein = ADP + a phosphoprotein.