PROTEIN PHOSPHATASES ARE PEST CONTAINING PROTEINS

Protein phosphatases are required for removing phosphoryl groups in pr oteins involved in many physiological processes. Investigation of thes e enzymes for regions rich in proline (P), glutamic acid (E), serine ( S) and threonine (T), called PEST regions showed that greater than 85% of the phosphatases investigated contained these regions. These regio ns are believed to be signals for degradation and could possibly serve as regulators of the intracellular localization and catalytic activit y via limited proteolysis or as conditional signals for rapid degradat ion of these proteins by the ATP/ubiquitin-dependent and/or the ATP no n-ubiquitin dependent proteolytic pathway. Many of these phosphatases were also found to contain a pentapeptide sequence biochemically relat ed to the KFERQ motif which targets proteins for lysosomal degradation which suggest that several pathways may ex-ist for the degradation of protein phosphatases.