May phosphorylate cofilin-1 and induce actin polymerization through this process, during the late stages of embryogenesis. Involved in the TNF-alpha-induced signaling pathway. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Predominantly expressed in skeletal muscle during embryogenesis. Expression was detected in the myotome at 10.5 dpc and, thereafter, was observed in developing skeletal musculature from 11.5 to 13.5 dpc and increased from 15 to 17 dpc. However, expression in skeletal muscle was not observed in adults. Its expression may be down-regulated as development proceeds. Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. STE20 subfamily. Contaminating sequence. Potential poly-A sequence.