PROTEIN PHOSPHATASES - STRUCTURE AND FUNCTION (A REVIEW)

Phosphorylation of proteins and enzymes is crucial for cell growth, di fferentiation, division and mitosis. Phosphorylation causes conformati onal changes in a protein resulting in most cases in its increased enz ymic activity and in more efficient substrate binding. Phosphorylation is effected by a variety of protein kinases. These enzymes are classi fied as tyrosine and serine protein kinases in accord with the amino a cid residues to be phosphorylated. Earlier we have reviewed the data o n the structure and functions of tyrosine protein kinases [Mol. Biol., 27, 725-733 (1973)]. Here the functional significance and the structu re of protein phosphatases, which are antagonists of protein kinases, are considered.