Plant phosphopeptide-binding proteins as signaling mediators

Regulation of the activity, location, and interactions of proteins by phosphorylation is crucial for many cellular processes including regulation of signaling. Phosphorylation-dependent interactions between proteins are one outcome of phosphorylation that can contribute to that regulation. Several kinds of phosphopeptide-binding proteins have been characterized, but in plants only by the forkhead-associated (FHA) domain proteins and, predominantly, the 14-3-3 proteins exist. 14-3-3 proteins have been shown to interact with several different classes of phosphorylated target proteins throughout eukaryotes. Initially, plant 14-3-3s were thought to be primarily associated with metabolic enzyme regulation; however, recent years have seen an increasing number of reports describing roles of 14-3-3 proteins in signal transduction, with plant 14-3-3 proteins now shown to interact with key proteins in signaling pathways.