The 14-3-3 Protein Family, Beyond the Kinases and Phosphatases

Eukaryotic phosphorylation of serine and threonine residues is a central regulatory mechanism in cell signalling, carried out by more than 500 kinases and a diverse array of phosphatases. Traditionally understood as a two-component system driven by writers (kinases) and erasers (phosphatases), this regulatory network is now appreciated to involve additional proteins that modulate or interpret phosphorylation-dependent changes. Among them, the 14-3-3 protein family has emerged as a prominent example due to its ability to bind phosphorylated serine/threonine motifs—typically located within intrinsically disordered regions—and influence the activity, stability, or localization of its partners. In this review, we discuss the importance, evolution, structure, and dynamics of 14-3-3 proteins, as well as their interactions with small molecules—both natural and designed—that bind to them. We highlight several underexplored aspects of their molecular behaviour, integrate recent discoveries, and emphasize how these insights contribute to a broader understanding of phosphorylation-dependent regulation across eukaryotes.