ON TARGET WITH A NEW MECHANISM FOR THE REGULATION OF PROTEIN-PHOSPHORYLATION

There is overwhelming evidence that the reversible phosphorylation of proteins regulates most aspects of cell life. However, the broad speci ficities displayed by many protein phosphatases and kinases in vitro d ictates that their activities be strictly regulated in vivo. Recent ev idence indicates that a novel class of proteins, known as targetting s ubunits, specifies the location, catalytic and regulatory properties o f protein phosphatases and kinases, and thereby plays a key role in en suring the fidelity of protein phosphorylation.