P38 beta is a member of the MAP kinase subfamily of Ser/Thr protein kinases. MAP kinases act as an integration point for multiple biochemical signals, and are involved in a wide variety of cellular processes such as proliferation, differentiation, transcription regulation and development. This kinase is closely related to p38 MAP kinase, both of which can be activated by changes in osmolarity of the extracellular environment, proinflammatory cytokines and cellular stress. This protein preferentially phosphorylates transcription factor ATF2. It is activated by phosphorylation on threonine and tyrosine by MKK6, and inhibited by pyridinyl-imidazole related compounds. Highest levels of expression are found in the brain and heart, with additional expression in the placenta, lung, liver, skeletal muscle, kidney and pancreas.