The 14-3-3 proteins are a family of homologous. evolutionarily conserved. acidic proteins expressed in all eukaryotes. with molecular masses ranging from 28-33kD. To date. seven different 14-3-3 isoforms have been identified in mammals. each encoded by a distinct gene. The expression of 14-3-3 isoforms is tissue specific and differentially regulated. The 14-3-3 proteins assemble into stable homo- and heterodimers. which modulate signaling cascades by binding to phosphorylated serine or threonine residues of target proteins. In addition to a phosphorylated serine or phohsphorylated threonine residue. 14-3-3 protein binding also requires an arginine located at position 3 or 4. The 14-3-3 proteins affect signaling in several manners. including: interfering with protein/protein interactions (example: 14-3-3's interference