Emerging evidence supports the dual function of kinase suppressor of Ras 1 (KSR1) as an active kinase and a scaffold, although it has been extensively referred as a pseudokinase, due to the absence of key residues in its catalytic domain [1, 2]. As a scaffolding protein, KSR1 orchestrates the assembly of the protein kinases RAF, mitogen activated protein kinase (MAPK) kinase (MEK), and extracellular signal-regulated kinase (ERK) in the canonical Ras-RAF-MAPKs pathway, in a Ras-dependent manner or upon growth factor treatment [1, 3]. Conversely, structural and biochemical studies reveal that KSR1 is capable of phosphorylating MEK and more importantly, the catalytic activity of KSR is markedly increased when BRAF or inhibitor-bound CRAF is introduced in the complexes [1, 4, 5]. Such findings add complexity to th
