An increasing number of studies have proven that the kinase suppressor of Ras (KSR1) functions as a scaffolding protein that coordinates the assembly of a multiprotein complex containing mitogen-activated protein kinase and its upstream regulators. However, a few studies have reported that KSR1 can activate c-Raf-1. Therefore, whether KSR1 possesses a kinase activity has been an unresolved issue until now.
