Location-regulated scaffold connecting MEK to RAF. Has very low protein kinase activity and can phosphorylate MAP2K1 at several Ser and Thr residues with very low efficiency (in vitro). Acts as MAP2K1/MEK1-dependent allosteric activator of BRAF; upon binding to MAP2K1/MEK1, dimerizes with BRAF and promotes BRAF-mediated phosphorylation of MAP2K1/MEK1 (PubMed:29433126). Interaction with BRAF enhances KSR2-mediated phosphorylation of MAP2K1 (in vitro). Blocks MAP3K8 kinase activity and MAP3K8-mediated signaling. Acts as a negative regulator of MAP3K3-mediated activation of ERK, JNK and NF-kappa-B pathways, inhibiting MAP3K3-mediated interleukin-8 production. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Kinase activity is inhibited by ASC24. Heterodimerizes (via N-terminus) with BRAF (via N-terminus) in a MAP2K1/MEK1-dependent manner (PubMed:29433126). Interacts with BRAF; this increases the low intrinsic protein kinase activity of KSR2 (PubMed:21441910). Interacts with MAP2K1, forming a heterodimer that can dimerize to form a heterotetramer (PubMed:29433126, PubMed:21441910, PubMed:12975377). Interacts with MAP3K8, MAPK, RAS and RAF (PubMed:12975377). Mainly expressed in brain and kidney. The protein kinase domain is predicted to be catalytically inactive and seems to have very low intrinsic kinase activity. This low kinase activity can be increased by interaction with BRAF. Phosphorylated on Ser-474 by MARK3. Belongs to the protein kinase superfamily. TKL Ser/Thr protein kinase family. KSR2 binds ATP and has very low in vitro protein kinase activity; the physiological relevance of this activity is unknown. KSR2 is proposed to be in an inactive conformation by itself or in complex with MAP2K1. Interaction with BRAF is proposed to induce a conformation change that increases the low intrinsic kinase activity (PubMed:21441910).