Combinatorial control of the specificity of protein tyrosine phosphatases

Protein tyrosine phosphatases (PTPs), the enzymes that dephosphorylate tyro syl phosphoproteins, were initially believed to be few in number and serve a 'housekeeping' role in signal transduction. Recent work indicates that th is is totally incorrect. Instead, PTPs comprise a large superfamily whose m embers play critical roles in a wide variety of cellular processes. Moreove r, PTPs exhibit exquisite substrate specificity in vivo. Recent evidence ha s led us to propose that members of the PTP family achieve selectivity thro ugh different combinations of specific targeting strategies and intrinsic c atalytic domain specificity.