Acts as a scaffold for the formation of a ternary MAP3K2/MAP3K3-MAP3K5-MAPK7 signaling complex. Activation of this pathway appears to play a critical role in protecting cells from stress-induced apoptosis, neuronal survival and cardiac development and angiogenesis. 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] Interacts with PARD6A, MAP3K3 and MAPK7. Forms a complex with SQSTM1 and PRKCZ or PRKCI (By similarity). (Microbial infection) Interacts with Yersinia YopJ. Expressed in many adult tissues. Abundant in heart and skeletal muscle. Binds MAP3K2/MAP3K3 and MAPK7 via non-overlapping residues of the PB1 domain. This domain also mediates interactions with SQSTM1 and PARD6A (By similarity). Activated by phosphorylation on Ser/Thr by MAP kinase kinase kinases. (Microbial infection) Yersinia YopJ may acetylate Ser/Thr residues, preventing phosphorylation and activation, thus blocking the MAPK signaling pathway. Incomplete sequence. Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. MAP kinase kinase subfamily.