Phospho-MSK1 (Ser212) Antibody detects endogenous levels of MSK1 only when phosphorylated at Serine 212. an AGC kinase of the RSK family. Has two kinase domains connected by a regulatory linker region. Enzyme activity requires the presence of both kinase domains. Is phosphorylated and activated by Erk as well as p38 MAPK in response to growth factors and cellular stress.