MAP3K

MAP3Ks (Mitogen-activated protein kinase kinase kinases), the top components of MAPK cascades, modulate many biological processes, such as growth, development and various environmental stresses. Based on the sequence of their kinase catalytic domain, MAP3Ks are classified into three groups: the MEKK-like, ZIK-like and Raf-like families. Raf-like MAP3Ks constitute largest MAP3K subfamily. Raf-like MAP3Ks play roles in response to biotic and abiotic stresses.

MAP3Ks often bind to both MAP4Ks and MAP2Ks in the same pathway. For example, MEKK1 (MAP3K1) binds to both the MAP4K NIK and the MAP2K MKK4, while NSY-1 (MAP3K) binds to the MAP2K SEK-1. MAP3Ks activates MAP2Ks by phosphorylation of a serine and/or threonine, and MAP2Ks activate MAPKs by dual phosphorylation of a Thr-X-Tyr motif.