Twenty human proteins encode Phox/Bem1p (PB1) domains, which are involved in forming protein heterodimers. MEKK2, MEKK3, and MEK5 are 3 serine-threonine protein kinases that have PB1 domains. MEKK2, MEKK3, and MEK5 are the MAP3Ks and the MAP2K in the ERK5 mitogen-activated protein kinase (MAPK) signaling module. ERK5 is a critical MAPK for both development of […]