 As kinases are a major drug target and a major control point in cell behavior, the kinome has also been the target of large scale functional genomics with RNAi screens and of drug discovery efforts, especially in cancer therapeutics.In animals, the kinome includes kinases that phosphorylate only tyrosine (tyrosine kinases), those that act on serine or threonine, and a few classes, such as GSK3 and MAP2K that can act on both.Research has shown that there are specialized protein domains that bind to phosphorylated serine and threonine residues, such as BRCA and FHA domains.