PROTEIN-TYROSINE PHOSPHATASES IN SIGNAL-TRANSDUCTION

Protein-tyrosyl phosphorylation, regulated by protein tyrosine kinases and protein tyrosine phosphatases (PTPs), is a key cellular control m echanism. Until recently, little was known about PTPs. However, the pa st two years have witnessed an explosion of information about PTP stru cture, regulation and function. Crystal structures of several PTPs hav e provided insights into enzymatic mechanisms and regulation and sugge sted the design of 'substrate-trapping' mutants. Candidate hemophilic and heterophilic ligands for transmembrane PTPs have been identified, and roles for transmembrane PTPs in regulating cell-cell interactions have been suggested. Finally, progress has been made in understanding signaling by Sro homology 2 domain containing PTPs and PTPs controllin g yeast osmoregulatory pathways.