Protein Kinases and Phosphatases in the Drosophila Genome

The reversible phosphorylation of proteins on serine, threonine, and tyrosine residues represents a fundamental strategy used by eukaryotic organisms to regulate a host of biological functions, including DNA replication, cell cycle progression, energy metabolism, and cell growth and differentiation. Levels of cellular protein phosphorylation are modulated both by protein kinases and phosphatases. Although the importance of kinases in this process has long been recognized, an appreciation for the complex and fundamental role of phosphatases is more recent. Through extensive biochemical and genetic analysis, we now know that pathways are not simply switched on with kinases and off with phosphatases. Rather, it is the balance of phosphorylation that is often critical. Protein phosphorylation can regulate enzyme function, mediate protein–protein interactions, alter subcellular localization, and control protein stability. Furthermore, kinases and phosphatases may work together to modulate the strength of a...