There are 7 STAT proteins: STAT1, STAT2, STAT3, STAT4, STAT5A, STAT5B and STAT6.[1] STAT proteins contain many different domains, each with a different function, of which the most conserved region is the SH2 domain.[2] The SH2 domain is formed of 2 α-helices and a β-sheet and is formed approximately from residues 575–680.[2][3] STATs also have transcriptional activation domains (TAD), which are less conserved and are located at the C-terminus.[4] In addition, STATs also contain: tyrosine activation, amino-terminal, linker, coiled-coil and DNA-binding domains.[4]