The 14.3.3 proteins are a family of highly homologous proteins that are encoded by separate genes and expressed in all eukaryotic cells, which exhibit a remarkable degree of sequence conservation between species and share a few basic biochemical properties. The 14.3.3 proteins bind to and regulate a broad range of cellular signaling proteins, including kinases, phosphatases and trans-membrane receptors. One proposed mechanism reveals that a conserved amphipathic groove in the chemical structure of the 14.3.3 proteins possibly mediates their interaction with the phosphoamino acid in target proteins. The 14.3.3 proteins are abundant in the brain and also present in all tissues (such as testes, liver and heart), which are involved in a wide range of vital regulatory processes, including mitogenic signal transduction, apoptotic cell death and cell cycle control.