Location-regulated scaffolding protein connecting MEK to RAF. Promotes MEK and RAF phosphorylation and activity through assembly of an activated signaling complex. By itself, it has no demonstrated kinase activity.
Belongs to the protein kinase superfamily. TKL Ser/Thr protein kinase family. Contains 1 phorbol-ester/DAG-type zinc finger. Contains 1 protein kinase domain.
Phosphorylated on Ser-309 and, to a higher extent, on Ser-404 by MARK3. Dephosphorylated on Ser-404 by PPP2CA. In resting cells, phosphorylated KSR1 is cytoplasmic and in stimulated cells, dephosphorylated KSR1 is membrane-associated.
Cytoplasm. Membrane. In unstimulated cells, where the phosphorylated form is bound to a 14-3-3 protein, sequestration in the cytoplasm occurs. Following growth factor treatment, the protein is free for membrane translocation, and it moves from the cytoplasm to the cell periphery.