TGF-beta-activated kinase 1 (TAK1; also MAP3K7) is a member of the STE Ser/Thr protein kinase family and the MAP kinase kinase kinase subfamily. Human TAK1 is 606 amino acids (aa) in length and contains a protein kinase domain at aa 36-291. There are three isoforms for TAK1. Isoform 1B is the largest isoform. Isoform 1A has a 27 aa deletion corresponding to aa 404-430 in isoform 1B, and isoform 1C has an 88 aa deletion corresponding to aa 519-606 in isoform 1B. TAK1 activity has been implicated during TGF beta-induced and Ras-dependent tumorigenesis.