Serine/threonine kinase required in the early embryo for the formation of terminal structure (PubMed:3135183, PubMed:8423783). Also required during the proliferation of imaginal cells (PubMed:3135183). May act downstream of Ras85D in the tor signal transduction pathway (PubMed:8423783). During larval development, mediates Ptth/tor signaling leading to the production of ecdysone, a hormone required for the initiation of metamorphosis (PubMed:19965758). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Binds 2 Zn(2+) ions per subunit. In quiescent cells, maintained in an inactive state via an intramolecular interaction between the protein kinase and N-terminal domains (By similarity). Following mitogen-mediated cell activation, binds via its RGB domain to active Ras85D (GTP-bound) which releases the inhibitory intramolecular interaction between the two domains (By similarity). This allows the Dsor1/MEK1-mediated dimerization of ksr and Raf which activates Raf (PubMed:29433126). Interacts with Dsor1/MEK1 and ksr; Dsor1 binding to ksr probably promotes ksr and Raf dimerization and ksr-mediated Raf transactivation. Expressed both maternally and zygotically. Zygotically expressed throughout embryogenesis. Extensively phosphorylated 1 to 2 hours after egg laying. RNAi-mediated knockdown in the prothoracic gland (PG) delays the onset of pupariation by prolonging the L3 larval stage. Belongs to the protein kinase superfamily. TKL Ser/Thr protein kinase family. RAF subfamily.