MEKK1: Proteins and Enzymes

MEKKs (Mitogen activated protein kinase kinase kinases) are serine-threonine kinases that act as the first tier of cellular MAP kinase pathways by activation of MAP/ERK kinases, or MEKs. Many enzymes with MEKK activity have been identified, including MEKK1-4, Raf, MLK3, TAK, and DLK. MEKKs generally display little similarity outside of their catalytic kinase domains. MEKK1-4 are nearly 50% identical within their catalytic domains, and are known to regulate Erk, Jnk, and p38 MAP kinase pathways. MEKK2 and MEKK3 bind MEK5 via conserved PB1 domains, leading to downstream activation of Erk5.