Membrane-associated protein kinase that phosphorylates on serine and threonine residues. In vitro substrates include DRG1, ENO1 and EIF4EBP1. Also autophosphorylates (By similarity). May be involved in secretory vesicle trafficking or intracellular signaling. May have a role in regulating stromal-epithelial interactions that occur during ductal morphogenesis in the mammary gland. May be involved in TGF-beta signaling. Able to autophosphorylate on Tyr residue; it is however unclear whether it has tyrosine-protein kinase toward other proteins. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Monomer. Interacts with DRG1 (via its N-terminal); the interaction phosphorylates DRG1. Associates with Golgi and Golgi-derived vesicles. Expressed in heart, liver, brain, spleen, lung, skeletal muscle, kidney and testis. By TGF-beta. Mainly autophosphorylated on serine/threonine residues. Also autophosphorylated on Tyr-198 (By similarity). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.