Site-specific incorporation of a phosphotyrosine mimetic reveals a role for tyrosine phosphorylation of SHP-2 in cell signaling

The regulation of protein tyrosine phosphatase (PTPase) SHP-2 is proposed t o involve tyrosine phosphorylation on two tail tyrosine residues. Using "ex pressed protein ligation", nonhydrolyzable phosphotyrosine analogs were int roduced at known phosphorylation sites in SHP-2. Biochemical analysis sugge sts that a phosphonate at Tyr542 interacts intramolecularly with the N-term inal SH2 domain to relieve basal inhibition of the PTPase, whereas a phosph onate at Tyr-580 stimulates the PTPase activity by interaction with the C-t erminal SH2 domain. Microinjection experiments indicate that a single phosp horylation of Tyr-542 of SHP-2 is sufficient to activate the MAP kinase pat hway in living cells. These studies support a novel mechanism explaining ho w tyrosine phosphorylation of a PTPase is important in signal transduction.